GLOSSARY A READING ROOM OF IDEAS REASONED ALOUD

Every term the collection defines.

4126 terms, gathered from the key-terms station of every explanation and linked back to the piece that defines each one.

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4126 terms

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1-MCP: A compound that occupies ethylene receptors without triggering them, used commercially to hold fruit unripe.DEFINED IN Ripening by contagion
2/10 net 30: Terms offering a two per cent discount for payment within ten days, with the full amount otherwise due at thirty.DEFINED IN Trade credit
429 Too Many Requests: The HTTP status for a rate-limited request, defined in RFC 6585 and paired with Retry-After.DEFINED IN Rate limiting
__Host-` prefix: A cookie naming convention browsers enforce, requiring Secure, no Domain attribute, and Path=/, pinning the cookie to one host.DEFINED IN Continuity over a protocol with no memory

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A-D strip: A dye-coated indicator strip placed in a film can, whose colour change estimates the free acidity in the enclosed air.DEFINED IN Vinegar syndrome
Abduction: Inference to the best explanation, which yields plausible rather than certain conclusions.DEFINED IN Recovering what the business meant
Ablation: The vaporisation and removal of a body's surface material by intense heating during entry.DEFINED IN Meteor streaks · Reentry heating
Abscisic acid: The hormone that accumulates under water stress and drives guard cells to lose turgor, closing the pore.DEFINED IN Midday stomatal closure
Abscission layer: The band of cells at the base of the leaf stalk that seals the leaf off andDEFINED IN Why do leaves change color?
Absolute advantage: Producing a good with fewer inputs than another producer; notably not what decides who should specialise in it.DEFINED IN Comparative advantage
Absolute risk reduction (ARR): The difference in event rates between treated and untreated groups, in percentage points.DEFINED IN Number needed to treat
Absorption: The fraction of incident sound energy a surface, an object or an audience converts to heat rather than reflecting.DEFINED IN Concert hall reverberation
Abstract artefact: A fictional character understood as a real object created by an author's activity.DEFINED IN Talking about what does not exist
Abstract machine: The idealised execution model a language standard describes, which a compiler must match in observable behaviour only.DEFINED IN Undefined behaviour
Accelerated ageing test: A vigour test exposing seed to heat and humidity to compress storage deterioration before germinating it.DEFINED IN Seed vigour versus germination
Acceleration: Moving a highly able student to more advanced material or an older cohort rather than to a differently taught class.DEFINED IN Ability grouping
Acceptance: Voluntarily taking a proposition as a premise for reasoning without holding it true.DEFINED IN Believing at will
Accepted difference: A divergence deliberately kept, recorded with the reason and date it was agreed.DEFINED IN Running both and comparing
Access-Control-Allow-Origin: The response header by which the far server names which origins may read its reply.DEFINED IN CORS in the web
Accountability: Answerability for an outcome, which unlike a task cannot be shared or delegated away.DEFINED IN Three kinds of responsible person
Accounting method: Proving an amortized bound by overcharging cheap operations and spending the stored credit on expensive ones.DEFINED IN The occasionally expensive operation
Accretion: The gain in surface height from newly deposited sediment.DEFINED IN Delta subsidence · River boundaries that shift
Accretion disc: The in-spiralling ring of gas around a compact object, heated until it radiates X-rays.DEFINED IN What is a black hole?
Accrual accounting: Recognising revenue when earned and costs when incurred, regardless of when cash moves.DEFINED IN Profit versus cash
Accuracy: Whether a value corresponds to the real-world fact it claims to represent.DEFINED IN Wrong with nothing missing
ACL staleness: The gap between a permission change at the source and its reflection in the index.DEFINED IN Permission-aware retrieval
Act consequentialism: The view that the right act is the one with the best consequences, assessed act by act.DEFINED IN Keeping a rule against the case
Acting from duty: Kant's condition on moral worth, contrasted with acting from a helpful inclination.DEFINED IN Effortless virtue
Action surface: The full set of operations an assistant can initiate, and how distinguishable they are.DEFINED IN Tool granularity
Activation energy: The energy barrier between reactants and products that a collision must surmount for reaction to occur.DEFINED IN Catalysis
Activation function: The non-linear step between layers, without which any depth of network reduces to a single linear layer.DEFINED IN How does a neural network learn?
Active and break phases: The alternating wet and pause spells within a monsoon season, driven by shifts in where convection organises.DEFINED IN Monsoon
Active layer: The surface layer above permafrost that thaws each summer and refreezes each winter.DEFINED IN Patterned ground
Active optics: The slow loop correcting the telescope's own flexure by commanding force actuators behind the mirror.DEFINED IN Large mirror flexure
Active Record: The alternative pattern in which a class both carries the domain behaviour and knows how to read and write its own row.DEFINED IN Objects that do not know they are stored
Active sensor: One that must emit energy to detect anything, as against a passive sensor that only listens.DEFINED IN Emissions control
Active site: The pocket where the substrate binds and the reaction happens.DEFINED IN Enzyme specificity
Actor-observer asymmetry: The proposed general tendency to explain one's own acts situationally and others' dispositionally; substantially weakened by later meta-analysis.DEFINED IN Attribution asymmetry
Acts and omissions doctrine: The claim that there is a morally significant difference between bringing about a harm and failing to prevent it.DEFINED IN Doing versus allowing
Acyl-homoserine lactone: The autoinducer class used by Vibrio fischeri and many related bacteria.DEFINED IN Quorum sensing
Adaptation lag: The interval between a new capability appearing and the opponent's response taking effect, which sets how much the first use is worth.DEFINED IN Fading advantage of a new weapon
Adapter: A concrete implementation of a port, holding all the technology-specific detail on the outside of the boundary.DEFINED IN Dependency direction
Adaptive model: The Bayesian procedure that narrows an athlete's expected range as their own sample history accumulates.DEFINED IN Athlete biological passport
Adaptive overfitting: The slow leakage of test-set information into design decisions through repeated evaluation by a whole community.DEFINED IN Benchmark saturation
Additive measure: A fact that can be summed across every dimension without becoming nonsense.DEFINED IN What one row stands for
Additive mixing: Combining light sources, so spectral powers sum and the result is brighter.DEFINED IN Color mixing
Adhesion: Attraction holding two unlike materials together at their interface.DEFINED IN Adhesion
Adiabatic: A change in which no heat crosses the parcel's boundary, so temperature changes only through work done or received.DEFINED IN Cooling with altitude
Adjacency list: Storing one parent reference per row; minimal storage, recursive reads.DEFINED IN A tree in a table of rows
Adjuvant: An ingredient that supplies the alarm signal a purified antigen lacks, so the response is mounted at all.DEFINED IN How vaccines work
Advanced glycation end-products: The durable modified proteins that result, and the ligands for a receptor that signals to the cell.DEFINED IN Diabetic complications
Advection fog: Fog formed when air moves horizontally over a surface colder than its dew point.DEFINED IN Coastal fog belts
Advection freeze: Freezing caused by the arrival of a cold air mass rather than by local radiative loss.DEFINED IN Radiation frost
Adversarial input: An input constructed specifically to trigger an algorithm's worst case, given knowledge of its rules.DEFINED IN Shuffling before sorting
Adversary-in-the-middle phishing: A proxy that relays credentials and codes to the real site in real time and captures the resulting session.DEFINED IN Why a code sent to your phone does not stop phishing
Adverse selection: Hidden information before contracting, so the parties who choose to trade are the costliest ones.DEFINED IN Adverse selection · Who leaves first
Aeronautical revenue: Income from airlines: landing, parking and per-passenger charges, often regulated.DEFINED IN Airport layout
Affirming the consequent / denying the antecedent: Their two invalid mirror images, inferring PDEFINED IN What makes an argument logically valid?
Aftermarket: The market for consumables, parts and service tied to a durable good already sold.DEFINED IN Aftermarket pricing
Age value: Riegl's term for the worth attached to visible evidence of the passage of time, as distinct from historical or artistic worth.DEFINED IN Patina and age value
Agenda control: The power to fix the order of pairwise votes, and thereby the outcome.DEFINED IN Cyclic majorities
Agent loop: The cycle of model output, tool execution, observation, and renewed model call.DEFINED IN The agent loop
Agent-centred prerogative: Scheffler's term for a permission to weight your own interests above what impartial maximising would allow.DEFINED IN Supererogation
Agent-regret: The distinctive regret felt by someone causally involved in a harm they were not to blame for.DEFINED IN Moral luck
Agglomeration economies: The advantages of many related activities being close together, which make a concentration self-reinforcing and outlast the reason it began.DEFINED IN City location · Industrial district persistence · Retail clustering
Aggregate: A crumb of soil bound by roots, fungal hyphae and microbial secretions, whose interior pores are largely unreachable by decomposers.DEFINED IN Soil carbon loss under ploughing
AIMD: Additive increase, multiplicative decrease: grow the sending rate gently while things work, halve it on loss.DEFINED IN Congestion collapse
Air change rate: How many times per hour a room's volume of air is replaced from outside.DEFINED IN House dust
Air seeding: Entry of air into a working conduit through a pore in a shared pit membrane, from a neighbour already embolised.DEFINED IN Cohesion-tension sap ascent
AIRE: A transcription factor making thymic cells display tissue-restricted proteins so clones against them can be tested.DEFINED IN Autoimmunity
Airport acceptance rate: The number of arrivals per hour an airport can safely take under current conditions.DEFINED IN Ground delay programs
Airside: The part of a terminal beyond security screening, accessible only to screened passengers and staff.DEFINED IN Airport layout
Akrasia: Acting intentionally against one's own better judgement.DEFINED IN Weakness of will
Albedo: The fraction of incoming sunlight a surface reflects rather than absorbs.DEFINED IN Urban heat islands
Aleatoric uncertainty: Irreducible randomness or ambiguity in the data itself, which more data cannot remove.DEFINED IN Confident model errors
Alert storm: One underlying fault producing many simultaneous alerts across dependent components.DEFINED IN Alert fatigue
Alexithymia: Persistent difficulty identifying and describing one's own emotions.DEFINED IN Interoception
Algorithm confusion: An attack in which a verifier is persuaded to use an unintended signature algorithm, such as verifying an RSA-signed token as an HMAC.DEFINED IN A valid token in the wrong place
Alias: Two effects estimated by the identical contrast, and therefore inseparable within that design.DEFINED IN Confounded factorial effects
Alias resolution: Deciding which differently named fields refer to the same underlying concept.DEFINED IN Six names for one field
Aliasing: The appearance of a frequency above half the sampling rate as a different, lower frequency in the record.DEFINED IN Aliasing
Alliance theory: Lévi-Strauss's account of marriage rules as systems of exchange binding groups together.DEFINED IN Marrying outside the group
Alliesthesia: Cabanac's term for an unchanged stimulus being felt as pleasant or unpleasant according to the perceiver's internal state.DEFINED IN Fasting
Allocation concealment: Keeping the upcoming assignment hidden from whoever enrols patients, so the sequence cannot be gamed.DEFINED IN Randomized trials
Allodynia: Pain produced by a stimulus that does not normally produce pain, such as light brushing.DEFINED IN Central sensitization
Allometry: The study of how a biological quantity changes with body size, usually as a power law.DEFINED IN Metabolic scaling
Alloreactivity: An immune response directed at another individual's tissue, notable for engaging an unusually large fraction of the T cell repertoire.DEFINED IN Transplant rejection
Allotrope: One of several distinct structural forms a single element can take.DEFINED IN Carbon allotropes
Allowed lateness: A declared grace period during which a window's state is retained so late events can produce a corrected result.DEFINED IN Event time versus arrival time
Alpha motor neuron: The cell whose firing drives the muscle fibres, and whose runaway output is the cramp.DEFINED IN Muscle cramp
Alternative stable state: A persistent condition, held by its own feedback, that a site can enter and not leave without a further shock.DEFINED IN Ecological succession · Gut colonization order
Ambient authority: Authority that applies automatically by context rather than being explicitly presented by the requesting party.DEFINED IN Requests you did not make
Amdahl's law: The 1967 observation that speed-up from parallelism is capped by the fraction of work that must be performed serially.DEFINED IN Vertical and horizontal scaling
Amendment rule: The provision specifying how a constitution may be changed, and by whom.DEFINED IN Constitutional entrenchment
Amenity migration: Movement toward places valued for landscape, climate or lifestyle rather than for work.DEFINED IN Rural depopulation
AMOC: The Atlantic Meridional Overturning Circulation, monitored across 26 degrees north since 2004.DEFINED IN Ocean circulation
Amortised cost: The average cost per operation over a worst-case sequence, which can be far lower than the worst single operation.DEFINED IN Counting steps instead of timing
Amortized cost: Total cost of any sequence of n operations divided by n; a worst-case bound on the total, involving no probability.DEFINED IN The occasionally expensive operation
Amphidromic point: A point in a basin about which the tidal wave rotates and at which the range of a given constituent is near zero.DEFINED IN Amphidromic points · Twice-daily tides
Amygdala: The structure that attaches emotional significance to experience, and one of the bulb's direct targets.DEFINED IN Smell and memory
Amylose / amylopectin: The linear and branched fractions of starch; the first recrystallises in hours, the second over days.DEFINED IN Bread staling
Analogical leveling: The extension of a dominant pattern to forms that resisted it, as whenDEFINED IN Why do languages change over time?
Analogy of being: Aquinas's rival account, on which terms apply to God truly but in a mode we cannot grasp.DEFINED IN Speaking of the unspeakable
Analytic and holistic marking: Scoring separate named criteria and summing them, versus judging the whole response at once.DEFINED IN Marker disagreement
Anarchy (in international relations): The absence of any authority above states able to enforce agreements between them.DEFINED IN Security dilemma
Anchor items: Questions common to two administrations, whose unchanged difficulty lets the cohorts be compared.DEFINED IN Exam equating
Anchorage: The massive block at each end that resists the main cable's horizontal pull.DEFINED IN Suspension bridge cables
Anchoring: Letting an available number set the reference point against which later judgements are made.DEFINED IN The dish nobody orders
Anchoring and insufficient adjustment: Estimating another mind by starting from your own and correcting too little.DEFINED IN Curse of knowledge in teaching
Angle cock: A manual valve at each vehicle end; if wrongly closed, it isolates the rest of the train from the driver's brake command.DEFINED IN Fail-safe braking
Angoff method: A procedure summing panellists' estimated success probabilities for a minimally competent candidate on each item.DEFINED IN Cut scores on licensing exams
Angular diameter: How wide something appears measured as an angle; the Moon's is about half a degree, whatever its altitude.DEFINED IN Moon illusion
Angular momentum: Moment of inertia multiplied by spin rate, conserved when no outside torque acts.DEFINED IN Figure-skating spin · Gyroscopic precession
Angular momentum transport: The movement of rotation from a star's core to its envelope by magnetic stresses and waves; its efficiency is measured but not yet explained.DEFINED IN Pulsar spin rates
Angulation: Bending at hip or knee so the edge angle differs from the body's inclination.DEFINED IN Carving ski sidecut
Aniconism: The practice or rule of not depicting the divine in figurative images.DEFINED IN Prohibition of images
Anionic polymerisation: Chain growth in which the site carrying the chain forward is a negatively charged carbon.DEFINED IN Instant glue
Anisogamy: Reproduction using two gamete sizes, one large and provisioned, one small and numerous, which is what creates distinct sexes.DEFINED IN Cost of sexual reproduction
Annealed glass: Glass cooled slowly enough that no significant residual stress is retained; the untreated baseline.DEFINED IN Tempered glass
Annotation keyword: A schema keyword such as title, description or examples that carries information but never affects validity.DEFINED IN A schema read by two audiences
Anode: The region where metal atoms give up electrons and dissolve as ions.DEFINED IN Corrosion
Anode / cathode: The electrode where oxidation happens and the one where reduction happens; only the anode corrodes.DEFINED IN Sacrificial anodes
Anoikis: Programmed cell death triggered by loss of attachment to the extracellular matrix.DEFINED IN Metastasis
Anoxia: The absence of dissolved oxygen, typical of an isolated deep layer late in a stratified season.DEFINED IN Lake turnover
Anoxygenic photosynthesis: Photosynthesis using a donor other than water, here sulfide, so it releases no oxygen.DEFINED IN Redox banding in sediment
ANSI/SPARC three-schema architecture: A distinct 1975 framework dividing a database into external, conceptual and internal schemas.DEFINED IN Drawing the same model three times
Antagonist co-contraction: Simultaneous activation of the opposing muscle, which stabilises a joint at the cost of net force.DEFINED IN Early strength gains
Antagonistic pleiotropy: Williams's account: alleles favoured for early benefits despite later costs.DEFINED IN Senescence
Antarctic Bottom Water: The densest water mass in the world ocean, formed when shelf water cascades down the continental slope.DEFINED IN Sea-ice brine rejection
Anthocyanins: Red and purple pigments produced in some autumn leaves.DEFINED IN Why do leaves change color?
Anti-alias filter: An analogue filter before a converter, removing content that would otherwise fold.DEFINED IN Aliasing
Anti-entropy: A background process that compares replicas and repairs differences, so convergence does not depend on every real-time message arriving.DEFINED IN Eventual consistency
Anti-reductionism: The view that testimony is a basic source of justification, giving a default entitlement that reasons for doubt defeat.DEFINED IN Knowledge from testimony
Anti-tail: An apparent sunward spike seen when Earth crosses the orbital plane and views a sheet of large, unpushed grains edge-on.DEFINED IN Comet tails
Anti-windup: Any scheme that stops or reverses integral accumulation while the actuator is saturated.DEFINED IN Integrator windup
Antibiotic stewardship: Coordinated use of antibiotics only when and as needed.DEFINED IN How does antibiotic resistance develop?
Antibody: A protein the body makes to latch onto a specific antigen.DEFINED IN How vaccines work
Anticipation: Producing an element of the target sentence before the corresponding source element has been uttered, licensed by context rather than signal.DEFINED IN Simultaneous interpreting
Anticorruption layer: A translation layer a context builds at its own edge so a foreign model cannot leak into its core.DEFINED IN Bounded contexts
Antigen: A structure on a cell surface that an antibody can bind, here a sugar chain (ABO) or a protein (RhD).DEFINED IN Blood compatibility · How vaccines work
Antigenic drift: The gradual accumulation of mutations in a virus's surface proteins that erodes recognition by existing antibody.DEFINED IN Original antigenic sin
Aperiodic: Not confined to returning only at multiples of some period, which is what allows convergence rather than oscillation.DEFINED IN Long-run chain behaviour
Aperture leakage: The field that escapes through a hole or slot in a shield, rising steeply once the opening approaches the wavelength.DEFINED IN Faraday cage
Aperture synthesis: Building up coverage of many baselines, aided by Earth's rotation, so an image can be reconstructed.DEFINED IN Radio interferometry
Apophatic (negative) theology: The approach that proceeds by denying attributes rather than affirming them.DEFINED IN Speaking of the unspeakable
Apoptosis: Regulated self-dismantling in which the cell shrinks, packages itself, and is eaten without inflammation.DEFINED IN Programmed cell death
Aposematism: Conspicuous appearance advertising a genuine defence such as toxicity, which predators learn to avoid.DEFINED IN Conspicuous signals
Apparent wind: The true wind combined with the headwind of the boat's own motion.DEFINED IN Sailing upwind
Appearance of bias: The objective test asking what an informed outside observer would conclude, as distinct from whether the judge is in fact partial.DEFINED IN Judicial recusal
Append-only storage: Storage that permits new entries but not modification or deletion of existing ones.DEFINED IN The audit record as the product
Apportionment: The allocation of legislative seats among regions in proportion to their counted populations.DEFINED IN Census undercount
Approval gate: A control that blocks an action until a human authorises it, enforced in the tool layer rather than by instruction.DEFINED IN Autonomy as a dial
Approximate nearest neighbour (ANN): An index that finds near vectors quickly by accepting a small chance of missing the true nearest.DEFINED IN Caching an answer nobody asked for exactly
Aragonite and calcite: Two crystal forms of calcium carbonate used by different organisms; aragonite is the more soluble, so its users are affected first.DEFINED IN Ocean acidification
Arbitrary and capricious review: The court's inquiry into whether the agency gave reasons connected to the record, as distinct from whether the rule was wise.DEFINED IN Notice-and-comment rulemaking
Arbuscular mycorrhiza: The ancient and most widespread association, in which fungal structures branch inside root cortical cells to exchange nutrients.DEFINED IN Mycorrhizal carbon trade
Archimedes' principle: The upward force on a submerged or floating body equals the weight of the fluid it displaces.DEFINED IN Buoyancy
Arching: A load-bearing bridge of bodies or grains across an opening, which tightens under additional force instead of yielding.DEFINED IN Crowd crush
Area denial: Making a space too costly or too uncertain to use, without needing to control it.DEFINED IN Mine warfare
Areal unit: A bounded zone (tract, ward, postcode) that point-level data are aggregated into before publication.DEFINED IN Modifiable areal units
Argon rectification: The proposed mechanism by which a driven air bubble sheds reactive gases and stabilizes as essentially pure argon.DEFINED IN Sonoluminescence
Argument from ignorance: Treating absence of a disproof as support for a claim, or absence of proof as a disproof.DEFINED IN Burden of proof
Argument from silence: Inferring that something did not occur because a source fails to mention it, valid only where that source would be expected to mention it.DEFINED IN Historical silence
Arm's-length principle: The tax rule that related parties should price as unrelated parties would.DEFINED IN Internal transfer pricing
Armstrong limit: Roughly 19 kilometres, the altitude at which ambient pressure is low enough for body fluids to boil at body temperature.DEFINED IN Reentry heating
Arousal: The level of physiological activation a stimulus produces, distinct from which emotion is felt.DEFINED IN How can music create emotion?
Array efficiency: A farm's actual output divided by what the same machines would produce standing alone.DEFINED IN Wind farm wake losses
Arrow's impossibility theorem: The proof that no ranked voting rule can satisfy unrestricted domain, unanimity, independence of irrelevant alternatives and non-dictatorship at once for three or more options.DEFINED IN Voting rules
Articular cartilage: The hyaline cartilage covering the ends of bones in a joint; avascular, aneural and without lymphatics.DEFINED IN Cartilage healing
Asceticism: Deliberate self-denial undertaken for moral, spiritual or philosophical ends rather than a material result.DEFINED IN Fasting
Asperity: A microscopic peak on a real surface; contact between solids occurs at asperities.DEFINED IN Adhesion
Assemblage: The artefacts recovered together from one context, treated as one unit of analysis.DEFINED IN Ceramic seriation
Assertion keyword: A schema keyword such as type, enum or required that can make a document invalid.DEFINED IN A schema read by two audiences
Assertion test: A check that a named condition holds, such as uniqueness of a key or absence of nulls in a column.DEFINED IN Grade earned, not declared
Asset specificity: The extent to which an investment loses value outside a particular relationship, which is what creates lock-in.DEFINED IN Boundaries of the firm
Assimilation: Distortion of the whole account toward the teller's existing expectations and stereotypes.DEFINED IN Rumour sharpening
Assize (of weights and measures): The periodic inspection at which local measures were compared against sealed copies of a standard, and adjusted, stamped or destroyed.DEFINED IN Measurement standardization
Assortative mating: The tendency of partners to resemble one another on a trait more than chance pairing would produce.DEFINED IN Similar partners
Asteroseismology: Reading a star's interior rotation from its oscillation frequencies.DEFINED IN Pulsar spin rates
Asymmetric competition: Competition in which the larger individual pre-empts the resource rather than sharing it in proportion to size.DEFINED IN Forest height race
Asymmetric error cost: A decision setting in which one kind of mistake is far more expensive than the other, pulling the optimal threshold away from the midpoint.DEFINED IN Cosmetic produce standards
Asymmetric information: A transaction in which one side knows materially more about quality than the other.DEFINED IN Occupational licensing
Asymptote: A limit a curve approaches with ever-smaller increments without reaching it.DEFINED IN Falling records
Asymptotic analysis: Describing how cost grows as input size increases without limit, ignoring constants and lower-order terms.DEFINED IN Counting steps instead of timing
Asynchronous replication: Acknowledging a write once the primary has committed, without waiting for any replica.DEFINED IN Replication lag
At-least-once: Acknowledge after processing; work may be repeated, never lost.DEFINED IN Losing it or doing it twice
At-least-once / at-most-once: The two achievable delivery guarantees, differing in whether an uncertain send is retried.DEFINED IN Exactly once is a property of the pipeline
At-least-once delivery: A guarantee that no change is lost, but that some may be delivered more than once after a failure.DEFINED IN Change data capture
At-most-once: Acknowledge before processing; work may be lost, never repeated.DEFINED IN Losing it or doing it twice
At-will employment: An arrangement permitting dismissal without cause, the comparison case throughout.DEFINED IN Civil service tenure
Atomic clock: An extremely precise clock based on atomic transitions.DEFINED IN How does GPS find your location?
Atomic grain: The finest level at which the business process produces events, preserving every later question.DEFINED IN What one row stands for
Atomic pointer swap: The single indivisible write that makes a new snapshot current: the commit itself.DEFINED IN Transactions on immutable storage
Attached shadow: The dark region where an object's own surface has turned past ninety degrees from the light, as distinct from the shadow it casts elsewhere.DEFINED IN Stage lighting angle
Attachment anxiety and avoidance: The two continuous dimensions that adult attachment measures actually recover, underlying the familiar four labels.DEFINED IN Adult attachment patterns
Attack surface: The set of capabilities available to someone who gains execution inside the image.DEFINED IN Building somewhere you do not ship from
Attention as reinforcer: The observation that adult responsiveness itself functions as a reward for a young child, independent of whether the response is warm or cross.DEFINED IN Sibling regression
Attention head: One independent instance of the mechanism, with its own budget, run alongside others in the same layer.DEFINED IN Attention as a budget
Attention sink: The tendency to place leftover attention mass on a semantically empty position, usually the first token.DEFINED IN Attention as a budget · Lost in the middle
Attentional set: The description of what currently counts as relevant, which the selection process is tuned to.DEFINED IN Inattentional blindness
Attenuation: The proposal that unattended channels are weakened but still analysed, with each word's threshold deciding whether it surfaces.DEFINED IN Cocktail party effect
Attestation: A signed statement about how an artefact was produced, issued by the build platform.DEFINED IN Provenance of what you deploy
Attractor: The bounded set of states a dissipative dynamical system settles into wandering around.DEFINED IN Forecast horizon
Attribute-based access control (ABAC): Deciding access by evaluating policy over attributes of the user, resource and context.DEFINED IN Roles as compression
Attribution: The stricter requirement that a claim be entailed by the cited passage, not merely adjacent to it.DEFINED IN Citation without verification · Value of the original
Attrition: Loss of participants from a population over time; here the mechanism by which a training pattern shows up as an outcome.DEFINED IN Early sport specialization
ATU index: The Aarne-Thompson-Uther catalogue of recurring folk tale types across traditions.DEFINED IN Story shape
Audience (aud): The JWT claim naming the recipient a token is intended for; the recipient must check it against its own identifier.DEFINED IN A valid token in the wrong place
Audience binding: Restricting a token so only one named service will accept it, preventing replay elsewhere.DEFINED IN Blast radius
Audience costs: The domestic penalty a leader pays for publicly backing down, which makes public threats binding.DEFINED IN Escalation
Audience inhibition: Reluctance to act because a wrong judgement would be witnessed.DEFINED IN Bystander effect
Audit trail: An ordered record of actions with enough context to reconstruct what happened and under whose authority.DEFINED IN The audit record as the product
Auditability: The property of an answer that makes it cheap to check, distinct from the answer being correct.DEFINED IN Citation without verification
Auditory stream segregation: The process of parsing one mixed pressure wave into separate perceived sources.DEFINED IN Cocktail party effect
Auftragstaktik: The German term, roughly "mission-type tactics", for orders that fix the task and leave the method to the executor.DEFINED IN Mission command
Aura: Walter Benjamin's term for a work's unique presence in time and space, which he argued reproduction dissolves.DEFINED IN Value of the original
Auroral oval: The ring around each magnetic pole, near 65 to 70 degrees magnetic latitude, where precipitating electrons land.DEFINED IN Aurora
Austenite: The higher-temperature, higher-symmetry parent phase; the shape the alloy returns to.DEFINED IN Shape-memory alloys
Australian ballot: A state-printed ballot listing all candidates, issued at the polling place and marked in private.DEFINED IN Secret ballot
Authentication: Establishing, with evidence, that a party is the holder of that identifier, as of a particular moment.DEFINED IN Three questions people treat as one
Authorization: Deciding whether a given actor may perform a given action on a given resource, now.DEFINED IN Three questions people treat as one
Authorization code: A short-lived single-use value returned through the browser and exchanged directly for a token.DEFINED IN Delegation without the password
Autocatalysis: A reaction whose own product catalyses it, so its rate rises with the amount of product already formed.DEFINED IN Vinegar syndrome
Autocatalytic: Describing a process whose product promotes its own further production, hence self-accelerating once started.DEFINED IN Ripening by contagion
Autocatalytic process: One whose rate depends on the quantity of something it itself produces, so that its output is also its limiting input.DEFINED IN Training cadre bottleneck
Autoinducer: The small diffusible molecule a bacterium both secretes and detects, whose concentration serves as the reading.DEFINED IN Quorum sensing
Autologous transfusion: Reinfusing an athlete's own previously stored blood, leaving no foreign substance to detect.DEFINED IN Athlete biological passport
Autolysis: The breakdown of tissue by its own enzymes, which in fish softens the flesh without any microbial involvement.DEFINED IN Fish spoiling fast
Automatic disqualification: A category, usually direct pecuniary interest, that disqualifies without weighing.DEFINED IN Judicial recusal
Automatic imitation: The tendency for observing an action to speed the matching action and slow a mismatching one.DEFINED IN Contagious yawning
Automaticity: The state in which a practised skill runs without conscious control, and its component steps become unavailable to introspection.DEFINED IN Curse of knowledge in teaching · Deliberate practice · Experienced-worker injuries · Habit formation · Learning plateaus · Prerequisite chains
Automation bias: The tendency of human supervisors to accept an automated system's output and miss its errors.DEFINED IN Autonomy as a dial · Rubber-stamped review
Autoregressive: Generating each token given all preceding ones, which forces the serial ordering.DEFINED IN Prefill and decode
Autoregressive decoding: Generating a sequence one token at a time, each conditioned on its predecessors.DEFINED IN Speculative decoding
Autoregressive generation: Producing text one token at a time, each conditioned on all tokens before it.DEFINED IN One improbable word
Autoxidation: The self-sustaining radical reaction between a hydrocarbon and oxygen, propagated by peroxy radicals and branched by hydroperoxides.DEFINED IN Plastic weathering
Auxiliary assumptions: The background claims about instruments, samples and conditions needed to derive any prediction.DEFINED IN Scientific testability
Availability (in CAP): The strict form: every request to a non-failing node receives a non-error response.DEFINED IN The CAP theorem
Average density: An object's total mass divided by its total enclosed volume, including any air it contains.DEFINED IN Buoyancy
Average-case cost: Expected cost under an assumed distribution over inputs; a different and weaker kind of claim.DEFINED IN The occasionally expensive operation
Averted vision: The astronomical practice of looking slightly away from a faint object so its light falls on the more sensitive rod cells.DEFINED IN Self-defeating aims
AVL tree: A search tree keeping sibling subtree heights within one; height bounded near 1.44 log2 n.DEFINED IN A tree that rearranges itself
Avoidable cost: Expense that stops if a room is left empty: housekeeping, laundry, utilities, breakfast, commission.DEFINED IN Shoulder-season price cliff · Tourism seasonality
Avulsion: A river's abrupt abandonment of its channel, which can strand territory on the far side of a boundary.DEFINED IN Borders · River boundaries that shift
Award inventory: The seats an airline releases for redemption, controlled separately from seats sold for cash.DEFINED IN Frequent-flyer currency
Axial induction factor: The fraction by which a rotor slows the flow at its own plane; the far wake runs at one minus twice this.DEFINED IN Wind farm wake losses
Axial tilt (obliquity): The angle between Earth's rotation axis and the perpendicular to its orbital plane, currently about 23.4 degrees.DEFINED IN Seasons
Axis of action (the 180-degree line): An imaginary line through the scene; keeping the camera on one side preserves left-right screen direction across cuts.DEFINED IN Continuity editing
Azeotrope: A mixture whose boiling vapour has the same composition as the liquid, so distillation cannot change it.DEFINED IN Azeotropes

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B cell: The cell lineage that produces antibodies against a specific antigen.DEFINED IN How vaccines work
B-tree: A shallow balanced tree keeping entries in sorted order, the standard index structure.DEFINED IN Indexing
Babcock-Leighton mechanism: The regeneration of poloidal field from the decay of systematically tilted active regions.DEFINED IN Solar cycle
Back region: The setting where the activity is prepared and participants are unobserved.DEFINED IN Authenticity
Back-channel logout: The OpenID Connect flow where the provider sends each application a signed logout token server to server, without relying on the browser.DEFINED IN Signing out everywhere
Backchannel: A short response such as "mm" or "right", produced without any claim on the floor.DEFINED IN Conversation turn-taking
Backdoor / trigger: A rare input phrase associated during training with a specific output, dormant otherwise.DEFINED IN Poisoning the well
Backfill: Re-running a pipeline over historical periods to produce or correct their outputs.DEFINED IN Backfilling a pipeline · Lineage
Backfire effect: The proposed strengthening of a false belief by correcting it; famous, but largely unreplicated in later large-sample work.DEFINED IN Persistence of misinformation
Backpressure: Any mechanism by which a full or slow consumer signals upstream that production must stop or slow.DEFINED IN Backpressure
Backpropagation: Calculation of how each weight influences the loss, by applying the chain rule backwards through the layers.DEFINED IN How does a neural network learn?
Backscatter: The portion of scattered energy returned along the direction it arrived from, which is what a co-located transmitter and receiver can hear.DEFINED IN Stealth tradeoff
Backslopping: Carrying a portion of a finished ferment into the next batch as the inoculum.DEFINED IN Sourdough stability
Backward compatibility: A change a consumer written against the old schema can still read, such as adding an optional field.DEFINED IN Data contracts
Backward compatible: New code can read data written under the previous schema; upgrade consumers first.DEFINED IN Compatibility has a direction
Bacteroid: The differentiated, nitrogen-fixing form the rhizobia take inside a host plant cell.DEFINED IN Leghemoglobin in root nodules
Balance of probabilities: The civil standard: the account more likely than not prevails.DEFINED IN Standards of proof
Balancer: Veneer applied to a panel's hidden face solely to make the construction symmetrical.DEFINED IN Balanced veneer
Balancing test: The more common alternative, in which a judge weighs the seriousness of the breach against the value of the evidence.DEFINED IN Exclusionary rule
Ballast: Any series element, resistive or reactive, supplying enough positive differential impedance to stabilise a discharge.DEFINED IN Ballast in a gas discharge
Band gap: The minimum photon energy that can lift an electron from its bound state; below it, no electronic absorption occurs.DEFINED IN Glass transparency
Bandwidth feedback: Feedback given only when the error exceeds a set tolerance, so silence itself carries information.DEFINED IN Practice feedback
Bank (or wave): A clustered set of arrivals followed by departures at a hub, arranged so many connections work at once.DEFINED IN Missed connections
Bank or wave: A cluster of arrivals timed to land together so passengers can be re-sorted onto a cluster of departures.DEFINED IN Hub-and-spoke routing
Bargaining in the shadow of the trial: The idea that settlements cluster around the parties' shared estimate of the trial outcome, discounted by the cost avoided.DEFINED IN Plea bargaining
Bargaining range: The settlements both sides prefer to fighting, whose width equals the total cost of war.DEFINED IN Peace negotiation
Baroreceptor: A pressure sensor in the great vessels that fires with each heartbeat, giving cardiac signals their phasic timing.DEFINED IN Interoception
Barrier coating: A film that protects by excluding water, oxygen and ions rather than by reacting.DEFINED IN Self-healing coatings
Barriers to dissolution: The costs of leaving a relationship, distinct from how good the relationship is; the term that peer divorce moves.DEFINED IN Divorce contagion
Baryonic matter: Ordinary matter made of protons and neutrons, whose cosmic total is constrained by the abundances of light elements.DEFINED IN Galaxy rotation curves
Basal metabolic rate: Energy use of a resting, fasting animal at a comfortable temperature, distinct from its everyday field metabolic rate.DEFINED IN Metabolic scaling
Basal sliding: Motion of a glacier over its bed, requiring ice at the pressure-melting point and lubricating water.DEFINED IN Glacier flow
Base circle: The circle a tooth's involute is unwound from; the ratio is the inverse ratio of the two base radii.DEFINED IN Involute gear teeth
Base level: The lowest elevation to which a stream can cut, usually the sea or the trunk river it joins.DEFINED IN River capture
Base model: A model that has only been pretrained on next-token prediction, with no instruction or preference tuning.DEFINED IN Next-token prediction
Base rate: The underlying frequency of what is being looked for; the term that dominates how many alarms are false.DEFINED IN Randomized screening · Rubber-stamped review · Simpson's paradox
Baseline: The separation between two array elements, which sets the angular scale of the fringes they produce.DEFINED IN Radio interferometry · Releasing to a few first
Basic reproduction number: The average number of new infections one case produces in a fully susceptible population.DEFINED IN Virulence and transmission
Basis risk: The gap between what an index-triggered contract pays and what the buyer actually lost.DEFINED IN Catastrophe reinsurance
Bastion: An arrowhead-shaped projection whose flanks fire along the faces of neighbouring works.DEFINED IN Obsolete fortifications
Batch size: The amount of change bundled into a single release; the quantity this whole argument turns on.DEFINED IN Deploying more to break less
Batch window: The period available for a scheduled bulk process to complete before online service resumes.DEFINED IN Recovering a schedule nobody wrote down
Batesian mimicry: A harmless species resembling a defended one, exploiting a warning signal it does not back up.DEFINED IN Conspicuous signals
Bathtub curve: The composite shape of early-life, constant, and wear-out failure regimes plotted against age.DEFINED IN Preventive replacement · Warranty timing
Battleship curve: The tapered shape a type's frequency makes when plotted down a correctly ordered sequence.DEFINED IN Ceramic seriation
Bearer credential: A token whose mere possession grants access, with no further proof that the holder is the party it was issued to.DEFINED IN Continuity over a protocol with no memory
Bearer token: A credential granting access by possession alone, with no proof that the presenter is the party it was issued to.DEFINED IN Detecting a theft you cannot see
Beating: The pulsing in loudness produced by two components of nearly the same frequency, at a rate equal to their difference.DEFINED IN Musical consonance
Bedding plane: A surface within sedimentary stone where deposition changed, giving a weaker, more permeable direction.DEFINED IN Natural bed in stone
Belady's anomaly: The effect where increasing cache size increases misses, possible under first-in-first-out.DEFINED IN Choosing what to forget
Belady's MIN: The clairvoyant policy evicting the item used furthest in the future; optimal, and unimplementable.DEFINED IN Choosing what to forget
Belady's optimal policy: Evicting the entry whose next use is furthest away; optimal, but requires knowledge of the future.DEFINED IN Caching
Bellman-Ford: The slower alternative that tolerates negative edge weights and reports negative cycles.DEFINED IN Nearest first
Bend allowance: The true arc length of the bend along the neutral axis, added between the two tangent points.DEFINED IN Bend allowance
Bend deduction: The amount subtracted from the sum of the outside dimensions to give blank length.DEFINED IN Bend allowance
Bernoulli's principle: The relation between higher flow speed and lower static pressure along aDEFINED IN Shower curtain drift
Berth allocation: How a port assigns quay space and tender slots; often by request and historic precedent rather than by price.DEFINED IN Cruise call clustering
Best-of-seven series: A tie decided by the first to four wins between the same two entrants, used to enlarge the sample and reduce the influence of a single game.DEFINED IN Knockout upsets
Bet-hedging: A strategy that lowers average performance to reduce the chance of total loss, favoured when growth compounds across generations.DEFINED IN Bacterial dormancy · Weed seed banks
Beta: Prior information about a route's sequence of moves, whether described, filmed or read from chalk marks.DEFINED IN Climbing grade drift
Beta factor: The fraction of a component's failures attributed to common cause rather than to that unit alone.DEFINED IN Engineered redundancy
Beta meteoroid: A grain small enough that β exceeds about 0.5, leaving the solar system on an unbound trajectory.DEFINED IN Zodiacal dust replenishment
Beta movement: Apparent motion in which an object is seen travelling between two successively presented positions.DEFINED IN Apparent motion
Between-class tracking: Assigning students to different classes or streams by attainment, usually across most or all subjects.DEFINED IN Ability grouping
Betz's limit: The maximum fraction, 16/27 or about 59.3 per cent, of the wind's kinetic energy any open-flow rotor can extract.DEFINED IN Three-bladed turbines
Beveridge curve: The observed downward-sloping relationship between the vacancy rate and the unemployment rate.DEFINED IN Vacancies alongside unemployment
Beverloo's law: The discharge relation Q = C ρ √g (D − kd)^(5/2) for dry grains through an orifice.DEFINED IN Hourglass flow rate
Beyond reasonable doubt: The criminal standard, defined by the kind of doubt it excludes rather than by a probability.DEFINED IN Jury deliberation · Standards of proof
BF16: A 16-bit float with the same 8-bit exponent as FP32 and a 7-bit mantissa, trading resolution for range.DEFINED IN Model quantization
BGP (Border Gateway Protocol): How independently run networks advertise to each other which address blocks they can reach.DEFINED IN Internet packet routing
Bi-encoder: A model that encodes query and document separately into vectors, allowing document vectors to be precomputed and indexed.DEFINED IN Two-stage retrieval
Bias: Error from a model too constrained to represent the true relationship.DEFINED IN Overfitting
Biased estimator: An estimate deliberately shifted off the most likely value, because being wrong in one direction costs far more than the other.DEFINED IN Rules of thumb on site
Bicarbonate: The form most of the ocean's dissolved carbon takes, and what carbonate ions become when they absorb a proton.DEFINED IN Ocean acidification
Bid shading: Deliberately bidding below your own estimate, by an amount that should grow with both the noise in estimates and the number of bidders.DEFINED IN Winner's curse
Bifurcate merging: A terminology merging same-sex siblings of a parent with that parent while distinguishing the opposite-sex sibling.DEFINED IN Merged kinship terms
Big O, Big Theta, Big Omega: An asymptotic upper bound, a tight bound, and a lower bound respectively.DEFINED IN Counting steps instead of timing
Bijection: A pairing leaving nothing unmatched and nothing doubled up, in either direction.DEFINED IN Sizes of infinity
Bills of Mortality: London's weekly published counts of burials and christenings, analysed by Graunt from 1662.DEFINED IN Urban mortality
Binary heap: A complete binary tree with the parent-smaller property, stored implicitly in an array.DEFINED IN Half-sorted is enough
Binding energy: The energy equivalent of the mass defect; the work needed to disassemble the nucleus.DEFINED IN Nuclear binding energy
Binding energy per nucleon: Binding energy divided by mass number, the quantity whose curve peaks near iron-56.DEFINED IN Nuclear binding energy
Bio-banding: Grouping young athletes by maturity status rather than by birth year.DEFINED IN Junior champions
Bioavailability (F): The fraction of an administered dose reaching the general circulation intact; 1 by definition for an intravenous dose.DEFINED IN First-pass metabolism
Biofilm: A surface-attached community of cells embedded in secreted matrix, one of the behaviours these systems switch on.DEFINED IN Quorum sensing · Washing machine odour
Biogenic carbon: Carbon recently taken from the atmosphere by living things, whose return as carbon dioxide is accounted as near-neutral.DEFINED IN Landfill methane
Biological maturity: How far through growth and puberty a body actually is, which around adolescence can differ by years between children of identical chronological age.DEFINED IN Junior champions
Birefringence: Having different refractive indices for different polarisation directions, so polarisation can be rotated or delayed.DEFINED IN Liquid crystals
Birthday attack: An attack exploiting the fact that collisions in a hash of N possible values appear after about the square root of N attempts.DEFINED IN Birthday problem
Bitemporal model: Storing both the time a fact was true and the time the database believed it, so historical reports remain reproducible after a correction.DEFINED IN Late-arriving data · Point-in-time joins
Bivalence: The principle that every statement is either true or false, with no third option.DEFINED IN Vagueness
Bjerknes feedback: The mutual reinforcement between the east-west temperature contrast and the trade winds that maintain it.DEFINED IN El Nino oscillation
Bjerknes force: The net force on a bubble in an acoustic pressure gradient, which traps it at the antinode.DEFINED IN Sonoluminescence
Black Death: The plague pandemic that reached Europe in 1347 and killed a large share of the population within a few years.DEFINED IN Post-plague wages
Black film: A soap film thinned to far less than a wavelength, which reflects almost nothing because the two reflections cancel at every colour.DEFINED IN Soap film colours
Blackbody radiation: The continuous, temperature-determined glow of a hot dense body, independent of what it is made of.DEFINED IN Flame emission colours
Blackletter: The dense, angular script of early European printing, later narrowed to German use and later still to decorative borrowing.DEFINED IN Typeface voice
Blackstone's ratio: The maxim that it is better for ten guilty to escape than one innocent to suffer.DEFINED IN Presumption of innocence
Blameless postmortem: An incident review conducted so that participants can describe their actions and reasoning without fear of punishment, in order to surface the conditions that made the failure possible.DEFINED IN Blameless review
Blank: A sample containing none of the analyte, characterising the signal from nothing.DEFINED IN Detection limits
Blast radius: The number of systems, records, or people a single erroneous action can affect.DEFINED IN Autonomy as a dial · Blast radius · Bulkheads · Chaos engineering · Choosing the first piece to replace · Control plane and data plane
Blastema: The mound of proliferating, partly dedifferentiated cells that forms under a wound epidermis and rebuilds the missing structure.DEFINED IN Limits of regeneration
Bleaching: The light-driven straightening of the pigment's retinal molecule, which produces the visual signal and simultaneously puts that molecule out of service.DEFINED IN Dark adaptation
Bleed air: Hot compressed air tapped from an engine's compressor stage, cooled and used to feed the cabin.DEFINED IN Airplane cabin pressure
Bleed load: A resistor or capacitor across a lamp, absorbing leakage that would otherwise reach the driver.DEFINED IN Ghost glow in LED bulbs
Blinding: Keeping patients, clinicians or assessors unaware of the assigned arm, protecting the period after allocation.DEFINED IN Randomized trials
Block time: The scheduled time from leaving the departure gate to arriving at the destination gate.DEFINED IN Asymmetric flight times · Schedule padding
Block transfer: One contiguous read or write between disk and memory; the unit of cost in external-memory analysis.DEFINED IN Sorting more than fits
Blocked practice: Practising one type of item repeatedly before moving to the next type.DEFINED IN Interleaved practice
Blocking protocol: One in which a failure can leave correct participants unable to proceed safely until the failed component recovers.DEFINED IN The blocking commit
Bloom's 2 sigma problem: The 1984 finding, since not replicated at that size, that tutored students outperformed conventionally taught ones by about two standard deviations.DEFINED IN Tutoring versus class size
Blue ice field: An area of the ice sheet where sublimation and wind scour exceed snowfall, exposing old, dense, bubble-poor ice at the surface.DEFINED IN Antarctic meteorite concentration
Blunt-body principle: Allen and Eggers' result that a blunt shape detaches the shock and keeps most of the heated gas away from the vehicle.DEFINED IN Reentry heating
BM25: A refined ranking function adding term-frequency saturation and document-length normalisation.DEFINED IN Search indexing
Bodele Depression: A dry former lake bed in northern Chad, the most productive single mineral dust source on Earth.DEFINED IN Dust-fed rainforests
Body resonance: A frequency at which the instrument's plates and enclosed air respond strongly, and so radiate strongly.DEFINED IN Cello wolf tone
Boiling point: The temperature at which a liquid's vapour pressure equals the pressure above it, and therefore a function of that pressure.DEFINED IN Rolling boil versus simmer
Bone conduction: Transmission of sound to the inner ear through vibration of the skull and soft tissue rather than through the ear canal.DEFINED IN Voice recording mismatch
Bonferroni correction: Testing each of k hypotheses at α/k, which bounds the family-wise error rate at α for any dependence structure.DEFINED IN Testing many questions at once
Borda count: Points awarded by rank position, summed across all ballots.DEFINED IN Voting rules
Bore glazing: Hardened deposits filling the honed crosshatch of a cylinder liner, leaving a smooth surface that cannot control oil.DEFINED IN Light-load diesel running
Borrowing: Adopting a word or feature from another language.DEFINED IN Why do languages change over time?
Boserupian response: Intensification driven by population pressure: the reverse causal arrow.DEFINED IN New crops and population growth
Boundary layer: The thin film of nearly still air clinging to a surface, through which vapour must diffuse before the wider air can carry it off.DEFINED IN Evaporative drying · Golf ball dimples · Magnus effect
Boundary lubrication: The regime in which asperities touch and load is carried by thin chemical films rather than a fluid film.DEFINED IN Oil film in bearings
Boundary-value problem: A prediction whose answer depends on the constraints acting on the system; climate projection.DEFINED IN Forecast horizon
Bounded context: An explicit boundary within which a model applies and each term has exactly one meaning.DEFINED IN Bounded contexts
Bow shock: The standing compression wave ahead of a body moving faster than sound in the surrounding gas.DEFINED IN Reentry heating
Braiding: The splitting of a single tread into multiple parallel lanes across the same corridor.DEFINED IN Trail braiding
Brake pipe: The continuous air line running the length of a train, whose pressure carries the brake command inverted.DEFINED IN Fail-safe braking
Braking index: A measured number describing how a pulsar's spin-down depends on its spin, used to estimate its age and birth period.DEFINED IN Pulsar spin rates
Branch by abstraction: An abstraction layer inside a codebase that lets an implementation be swapped incrementally.DEFINED IN Replacing a system you cannot turn off
Branching step: A reaction producing more carriers than consumed.DEFINED IN Chain-branching explosion limits
Brand extension: Selling a new product under an established name, borrowing its reputation and exposing it.DEFINED IN Brand advertising
Brand salience: How readily a brand comes to mind in a buying situation, as distinct from any belief about its quality.DEFINED IN Uninformative advertising
Brandea: Objects, typically cloths, touched to a tomb or relic and held to acquire its power.DEFINED IN A relic proved false
Break of bulk: A point where cargo must be unloaded from one mode of transport and reloaded onto another.DEFINED IN City location · Fall-line cities
Breakage: Miles issued that are never redeemed, and therefore become margin.DEFINED IN Frequent-flyer currency
Breaking change: A change that invalidates existing consumers, requiring a version, a notice period, or a dual-serving window.DEFINED IN Data contracts
Brewster's angle: The incidence angle at which reflected and refracted rays are perpendicular and the in-plane polarisation is not reflected; tan θ equals the refractive index ratio.DEFINED IN Brewster angle glare
Bridewealth: Goods from the groom's kin to the bride's, compensating for her labour and securing rights in her children.DEFINED IN Bridewealth and dowry
Bright-line rule: A legal test fixed in advance in terms that can be applied without judgement about the case's merits.DEFINED IN Bright-line rules
Brine rejection: The exclusion of salt as sea ice forms, leaving the water beneath saltier and denser.DEFINED IN Ocean circulation · Sea-ice brine rejection
Brittle failure: Fracture with no appreciable deformation beforehand, so nothing warns of the limit being approached.DEFINED IN Marble supports
Broad money: The money the public can spend, dominated by commercial bank deposits rather than notes and coin.DEFINED IN Bank money creation
Brooks's law: The heuristic that adding manpower to a late software project makes it later.DEFINED IN Coordination cost
Bruck-Ryser-Chowla theorem: A number-theoretic condition ruling out certain symmetric designs, including projective planes of order 6.DEFINED IN Block design existence
Brythonic: The Celtic language spoken in Britain before English, source of many river names.DEFINED IN Place names
Budget window: The fixed span, commonly ten years in US practice, over which a bill's fiscal effect is officially estimated.DEFINED IN Budget scoring windows
Bufferbloat: Persistently high latency caused by oversized router buffers that absorb congestion instead of signalling it.DEFINED IN Congestion collapse
Build stage: An intermediate stage that runs the compiler and package manager and is not published.DEFINED IN Building somewhere you do not ship from
BuildKit: The current build engine, which resolves a build as a dependency graph and supports caches held outside the image layers.DEFINED IN Build cache geometry
Bulkhead: A partition of a shared resource that caps how much of it any one consumer can hold, so a failure is confined to that consumer.DEFINED IN Bulkheads
Bulla: A hollow clay ball enclosing tokens, sealed against tampering and sometimes impressed outside with the tokens within.DEFINED IN Writing invention
Bullwhip effect: The growth in order variability at each successive tier of a supply chain, above the variability of end-customer demand.DEFINED IN Bullwhip effect
Buoyancy: The upward force on a submerged body equal to the weight of fluid it displaces, which largely cancels a whale's weight.DEFINED IN Land size limits
Burden of proof: The obligation to support a claim, and by extension the allocation of who loses if the question stays unresolved.DEFINED IN Burden of proof · Jury deliberation · Presumption of innocence
Burgage plot: A long narrow urban holding running back from a street frontage, typical of medieval town grants.DEFINED IN Unplanned settlement form
Burn rate: How fast the budget is being consumed relative to the period, used to alert on trajectory rather than on a fixed threshold.DEFINED IN Error budgets
Burn-in: Deliberately operating units before delivery to precipitate the failure of defective ones.DEFINED IN Bathtub failure curve
Burr: The ridge of metal displaced but not removed by a drypoint needle, which shelters ink from the wipe.DEFINED IN Drypoint burr
Burstiness: The tendency of arrivals to cluster in time rather than spread evenly, here imposed by flight schedules.DEFINED IN Border queue surges
Bus bunching: The instability by which a late bus collects more passengers and falls further behind, while the following bus closes on it.DEFINED IN Inspection paradox
Busy beaver function: The greatest number of steps a halting machine of a given size can run; it grows faster than any computable function.DEFINED IN Halting problem
Buys Ballot's law: With your back to the wind, low pressure is on your left in the northern hemisphere.DEFINED IN Geostrophic wind
Buzz pollination (sonication): Shaking pollen from tube-shaped anthers by vibrating the flight muscles; done by many wild bees, not by honeybees.DEFINED IN Managed hives and wild pollinators
Bypassing: The passage of drift around a structure, either naturally once it fills or mechanically by pumping.DEFINED IN Downdrift beach loss
Bystander effect: The reduced likelihood that any given witness helps as the number of witnesses grows.DEFINED IN Bystander effect
Bystander selection: Selection pressure exerted by an antibiotic on colonising bacteria that are not the target of treatment.DEFINED IN Antibiotic course length
Byte-pair encoding (BPE): The algorithm that builds that vocabulary by repeatedly merging the most frequent adjacent pair of units.DEFINED IN Tokenization
Byzantine fault: A failure in which a node behaves arbitrarily or dishonestly rather than simply stopping.DEFINED IN Quorums

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C4 and CAM: Pathways that concentrate carbon dioxide around RuBisCO in space or in time, limiting photorespiration.DEFINED IN Photosynthesis
C:N ratio: The mass ratio of carbon to nitrogen in the feedstock, with about 30:1 the practical target for fast decomposition.DEFINED IN Compost heat
Cabin altitude: The altitude at which the cabin's pressure would be normal outside air; the figure the system actually controls.DEFINED IN Airplane cabin pressure · Inflight taste
Cache hit ratio: The fraction of requests answered at the edge without contacting the origin; it sets both speed and cost.DEFINED IN Content delivery networks
Cache key: The identifier a builder computes for a step, combining the parent state's identifier with the instruction and, for copies, a hash of the file contents.DEFINED IN Build cache geometry
Cache key collision: Two principals sharing a key because it omits the tenant, so one is served the other's data.DEFINED IN Warm reuse leaks
Cache line: The fixed-size block, commonly 64 bytes, that a cache tracks, transfers and owns as a unit.DEFINED IN False sharing · Fewer operations, slower program
Cache scope: The additional key material (user, tenant, model version, retrieved documents) that must match exactly for a stored answer to be reusable.DEFINED IN Caching an answer nobody asked for exactly
Cache-oblivious model: An analysis counting block transfers without being told the block size.DEFINED IN Fewer operations, slower program
Cadastre: The official register of land parcels, their boundaries and their holders.DEFINED IN Cadastral survey patterns
Cadre: The nucleus of experienced personnel around which a larger formation can be built.DEFINED IN Training cadre bottleneck
Calcium silicate hydrate: The nearly amorphous gel that makes up most of the binding phase in hardened cement paste.DEFINED IN Cement hardening
Calendar ageing: Capacity loss accruing with elapsed time regardless of use, accelerated byDEFINED IN Battery ageing
Calibration: The property that stated confidences match observed frequencies, so claims made at eighty percent are right about eighty percent of the time.DEFINED IN Confident model errors · Model routing
Calibration curve: The measured map from calendar year to radiocarbon age, built from tree rings and other dated archives.DEFINED IN Radiocarbon calibration plateaus
Call graph: A model of which routines can invoke which others, built by reading source rather than running it.DEFINED IN Code that never runs, and code that runs once a year
Callout or diagnostic fee: A charge for attending and identifying the fault, priced separately from the remedy so that the diagnosis is billed as the service it is.DEFINED IN Paying for the five-minute fix
Calvin cycle: The light-independent reactions that attach carbon dioxide to a five-carbon acceptor and build sugar.DEFINED IN Photosynthesis
Camp fever: The historical name for the epidemic illnesses of stationary armies, now understood mostly as typhus and enteric infections.DEFINED IN Siege camp attrition
Canary analysis: The automated comparison of the new version's metrics against a concurrently running baseline, used to promote or roll back.DEFINED IN Releasing to a few first
Candidate generation: The first, cheap stage whose job is recall at depth rather than precision at the top.DEFINED IN Two-stage retrieval
Cannibalisation: New revenue that displaces a firm's own existing revenue, reducing the project's net value to that firm alone.DEFINED IN Incumbent disruption
Canon: The set of works an institution treats as required, and therefore keeps in print, in translation and under commentary.DEFINED IN Canon formation
Canonical coin system: A set of denominations for which the largest-coin-first rule happens to be optimal.DEFINED IN When the best step now is safe
Canonical model: An agreed shared definition that participating systems map to and from.DEFINED IN Six names for one field
Canonisation: The institutional process by which a body of work becomes part of the accepted history of art.DEFINED IN Death and art prices
Cant: A vocabulary developed specifically to be unintelligible to outsiders, as distinct from one that merely becomes so.DEFINED IN Trade jargon
Cantor's diagonal argument: The proof that no list of reals is complete, by constructing a number differing from the nth entry in its nth digit.DEFINED IN Sizes of infinity
CAP theorem: The result that during a network partition a system must sacrifice either consistency or availability; it says nothing about the partition-free case.DEFINED IN Eventual consistency
Capability: A named, independently supported behaviour that a party declares it implements in full.DEFINED IN Capability negotiation · Isolation without a machine
Capacitance: The charge two conductors store per volt applied, set by their size, their separation, and the material around them.DEFINED IN Capacitive sensing
Capacitive coupling: Alternating current passing between two conductors separated by insulation, without contact.DEFINED IN Ghost glow in LED bulbs
Capacity fade / impedance rise: The two distinct failure modes: less charge stored, versusDEFINED IN Battery ageing
Capacity utilisation: The share of installed capacity actually in use, averaged over the year rather than at the peak.DEFINED IN Tourism seasonality
Capillary action: The movement of a wetting liquid into narrow spaces without external pressure, driven by surface tension.DEFINED IN Candle wick
Capillary limit: The heat load above which the wick cannot return liquid fast enough, at which point the evaporator dries out.DEFINED IN Heat pipes
Capillary rise: Upward movement of water through fine soil pores by surface tension, from a shallow water table toward an evaporating surface.DEFINED IN Salinization
Capital requirement: The minimum shareholder funds a bank must hold against its assets; the binding constraint in most modern systems.DEFINED IN Bank money creation
Capital stuffing: Investment in speed and capacity that redistributes a fixed catch rather than increasing it.DEFINED IN Race to fish under quota
Capitalisation: The conversion of a local amenity, such as school quality, into the price of housing that gives access to it.DEFINED IN Persistent poor neighbourhoods
Caramelization: The separate breakdown of sugar alone at higher temperatures, with no amino acid involved.DEFINED IN Maillard browning
Carbon equivalent: A formula combining carbon and alloying elements into one number for how readily a steel hardens on rapid cooling.DEFINED IN Delayed weld cracking
Carbonate-silicate cycle: The slow transfer of atmospheric carbon dioxide into rock by rainfall and weathering, and its return by volcanism; it requires liquid water.DEFINED IN Martian atmosphere loss
Carbonation: The reaction of atmospheric carbon dioxide with the concrete's alkalis, lowering pH and ending that protection.DEFINED IN Reinforced concrete
Carbonic acid: The weak acid formed when carbon dioxide dissolves in water; the agent that dissolves limestone.DEFINED IN Cave formation
Cardinality: The number of distinct time series a metric produces, equal to the product of its labels' distinct value counts.DEFINED IN Metric cardinality explosion · Sizes of infinity
Cardinality estimation: Predicting how many rows an operator will produce, the input on which plan costs depend.DEFINED IN Query plan estimation
Carmichael number: A composite that satisfies the Fermat condition for every base coprime to it; 561 is the smallest.DEFINED IN Compositeness without factors
Carotenoids: Yellow and orange pigments present in many leaves.DEFINED IN Why do leaves change color?
Carrier: The physical medium holding the bits, as distinct from their encoding.DEFINED IN Digital preservation churn
Carrying capacity: The level of use beyond which a site degrades or the experience fails; partly physical, largely a judgement about acceptable change.DEFINED IN Overtourism
Cascade: Running a cheaper model first and escalating to a stronger one only when its output fails a check.DEFINED IN Model routing
Case marking: An ending or particle on a noun that signals its grammatical role, such as subject or object.DEFINED IN Word order
Cash conversion cycle: The days between paying for inputs and collecting from customers; it can be negative.DEFINED IN Profit versus cash
Caspases: Protein-cutting enzymes held inactive in every cell that carry out the demolition once triggered.DEFINED IN Programmed cell death
Catalytic cycle: The sequence in which a catalyst binds, transforms, releases, and returns to its original form.DEFINED IN Catalysis
Cataphatic (affirmative) theology: The affirmative naming that apophatic method takes as its starting material.DEFINED IN Speaking of the unspeakable
Catastrophic forgetting: Loss of earlier capability when a network is trained hard on new data.DEFINED IN Fine-tuning versus retrieval
Catch per unit effort (CPUE): Catch divided by fishing effort, historically used as a proxy for abundance.DEFINED IN Fishery collapse
Catch rate: The fraction of genuinely bad items a reviewer stops; the only measure that separates a working control from a decorative one.DEFINED IN Rubber-stamped review
Cathode: The region where those electrons are consumed, in damp air by oxygen and water forming hydroxide.DEFINED IN Corrosion
Cathodic protection: Suppressing corrosion by holding a structure's potential low enough that its own metal will not oxidise.DEFINED IN Sacrificial anodes
Cauchy distribution: A heavy-tailed distribution with no finite mean or variance, whose sample averages never concentrate.DEFINED IN Ubiquity of the bell curve
Causal opacity: The property of a ritual act having no visible means-end connection to its stated outcome.DEFINED IN Ritual meaning
Causal tracing: Corrupting an input and restoring individual internal states to find which ones carry a fact.DEFINED IN Where a fact lives in a model
Cellular automaton: A lattice of cells updated in parallel by one rule reading a fixed local neighbourhood; the elementary family is one-dimensional with a three-cell neighbourhood, and has 256 members.DEFINED IN Cellular automata
Cellulose acetate: Film base made by converting cellulose's hydroxyl groups to acetate esters; the "safety film" that replaced nitrate stock.DEFINED IN Vinegar syndrome
Censored demand: Demand that exceeded available stock and therefore left no record, so observed sales understate what customers wanted.DEFINED IN Stockout demand censoring
Censoring: Observation of a case that ends before its outcome is known, which statistical methods can accommodate if it is modelled explicitly.DEFINED IN Survivorship bias
Cent: A logarithmic pitch unit defined so that an octave contains exactly 1200 of them.DEFINED IN Gamelan tuning
Central chemoreceptors: Brainstem sensors reading the acidity of cerebrospinal fluid, which tracks arterial CO2.DEFINED IN Breathing urge
Central limit theorem: The rescaled sum of many independent, finite-variance contributions approaches the normal distribution.DEFINED IN Ubiquity of the bell curve
Central place: A settlement supplying goods and services to a surrounding market area.DEFINED IN Town spacing
Central projection: Mapping each scene point to where the line joining it to a single viewpoint meets the picture plane.DEFINED IN Linear perspective
Central tolerance: Deletion or editing of strongly self-reactive lymphocytes as they develop in the thymus or bone marrow.DEFINED IN Autoimmunity
Cepheid variable: A pulsating star whose period correlates with its intrinsic brightness.DEFINED IN Cosmic distance ladder
Cercaria: The free-swimming or shed larval stage produced in huge numbers by asexual multiplication in the snail.DEFINED IN Parasite host manipulation
Cerebral oedema: Swelling of brain tissue as water moves into cells, constrained by the rigid skull.DEFINED IN Exercise-associated hyponatremia
Ceremony: A practice still performed after the problem it answered has changed or gone, recognisable by the absence of a stated live justification.DEFINED IN Ceremony as a smell
Cereulide: The heat-stable emetic toxin produced by Bacillus cereus, associated with rice left standing after cooking.DEFINED IN Leftover spoilage
Certificate: A signed statement from a trusted party binding a public key to an identity.DEFINED IN How encryption keeps messages secret
Certificate work: A work whose authentic form is a set of instructions plus a certificate of authenticity, so that any authorised execution counts as the work.DEFINED IN Value of the original
Certification: Protection of a title without restriction of practice; anyone may do the work, only the certified may claim the label.DEFINED IN Occupational licensing
Cession: Transfer of sovereignty over territory, usually subject to a heightened ratification requirement.DEFINED IN Enclaves
cgroup: A Linux control group: a hierarchy that accounts and limits a set of processes' use of memory, CPU and other resources.DEFINED IN Killed with memory to spare
Chain carrier: A short-lived radical whose reaction regenerates further carriers.DEFINED IN Chain-branching explosion limits
Chain scission: A break in the polymer backbone, reducing average molecular weight and with it toughness.DEFINED IN Plastic weathering
Chain-of-thought: Eliciting intermediate reasoning inside a single generation; distinct from chaining, which spans separate calls.DEFINED IN Prompt chaining
Chain-of-thought prompting: Eliciting intermediate reasoning steps in the output before the final answer.DEFINED IN Chain-of-thought
Challenge-response: A protocol in which the verifier issues an unpredictable value and the prover returns a response only the secret's holder could compute.DEFINED IN A secret you never send
Change blindness: The well-demonstrated failure to notice large changes to a scene when they occur during a saccade, blink or cut.DEFINED IN Continuity editing · Inattentional blindness
Change data capture: Observing and propagating every change made to a database, typically by reading its transaction log.DEFINED IN Change data capture · The outbox · Two systems, one record
Change data capture (CDC): Streaming a database's committed changes so another store stays current.DEFINED IN Replacing a system you cannot turn off
Change failure rate: The proportion of deployments that result in degraded service requiring a hotfix or rollback.DEFINED IN Deploying more to break less
Change propagation: The spread of a single edit into other modules that relied on what it changed.DEFINED IN Coupling
Changelog topic: A compacted topic holding changes to a local state store, used to rebuild it after a failure.DEFINED IN Keeping the history and the snapshot in one file
Changes: The fixed sequence of chords, with their durations, that a tune's improvisation follows.DEFINED IN Jazz improvisation
Channel: The route by which a report reached you, as distinct from its content; what a deception has to own, and what a defence has to price.DEFINED IN Strategic deception
Channel axis: The depth of minimum sound speed, about which trapped rays oscillate.DEFINED IN Deep sound channel
Channelling: The ridged buckling of the emulsion layer when the base beneath it shrinks and the emulsion does not.DEFINED IN Vinegar syndrome
Chaos Monkey: The Netflix tool, introduced in 2011, that randomly terminated production instances; the origin of the wider practice.DEFINED IN Chaos engineering
Characteristic path length: The typical number of edges on a shortest path between two nodes.DEFINED IN Small-world networks
Charge conservation: Charge is never created or destroyed, only moved, so any positive object implies an equally negative one somewhere.DEFINED IN Static electricity
Charge stacking: Bringing multiple charges from a single episode, raising the exposure a defendant faces if the case is tried.DEFINED IN Plea bargaining
Charm pricing: Setting a price just below a round figure, most often ending in 9, in the expectation of higher demand.DEFINED IN Charm pricing
Cheap signal: A signal costing the sender little to produce, and therefore weak evidence unless something bounds it.DEFINED IN Seating by the window
Checks and balances: Powers that allow institutions to restrain one another.DEFINED IN Why do democracies separate powers?
Chelate: A ligand binding one metal centre through two or more donor atoms, forming a ring that includes the metal.DEFINED IN Chelate effect
Chemical weathering: Alteration of minerals by water, acid and oxygen, notably feldspars becoming clays.DEFINED IN Soil formation
Chesterton's fence: The principle that a rule whose purpose is unknown should not be removed until the purpose is established.DEFINED IN Persistent rules
Childhood amnesia: The near-absence of retrievable memories from before about age three or four.DEFINED IN Reminiscence bump
Chilling injury: Damage to tissue held above freezing but below a species-specific threshold, accumulating with exposure time.DEFINED IN Chilling injury in fruit · Supermarket tomato flavour
Chiral: Describing an object, or molecule, that cannot be superimposed on its mirror image.DEFINED IN Molecular handedness
Chlorophyll: The green pigment that absorbs light for photosynthesis.DEFINED IN Why do leaves change color?
Choice set complexity: How far options differ on attributes that cannot be traded off on a common scale.DEFINED IN Choice overload
Chokepoint: The single place in a system through which a consequential action must pass, and therefore the only place a rule can be enforced rather than merely advised.DEFINED IN Guardrails · Maritime chokepoints
Chondrocyte: The sole cell type of cartilage, sealed within a lacuna in the matrix and unable to migrate through it.DEFINED IN Cartilage healing
Choreography: Coordination by reaction, where each participant publishes what it did and others subscribe, with no component holding the whole sequence.DEFINED IN Choreography versus orchestration
Chorus: One complete pass through the tune's form; the unit soloists count in.DEFINED IN Jazz improvisation
Chromatic dispersion: Pulse spreading caused by wavelengths travelling at slightly different speeds, which amplification does not correct.DEFINED IN Guided light in fibre
Chronic wound: A wound stalled in the inflammatory phase, failing to progress to proliferation.DEFINED IN Wound healing
Chunk: The unit of text that is indexed, scored, and returned by a retrieval system.DEFINED IN Chunking
Chunking: The reorganisation of several smaller units of action or perception into a single larger one.DEFINED IN Learning plateaus · Retrieval-augmented generation · Skilled diagnosis
Chuño: Andean potatoes freeze-dried by night frost and day sun, storable for years and warehoused by the Inka state.DEFINED IN Grain and taxation
Circadian phase: Where a body's internal daily cycle sits relative to clock time; a delay moves the whole cycle later without changing its length.DEFINED IN Teenage sleep phase
Circadian rhythm: An internally generated roughly twenty-four-hour cycle in physiology and behaviour, corrected daily against external cues.DEFINED IN Shift work
Circuit: An identifiable sub-computation inside a network that implements a specific step of a task.DEFINED IN Grokking in training
Circuit breaker: A control that stops sending requests to a failing dependency until it recovers.DEFINED IN Moving failure handling out of the program
Circuity: The extra distance flown relative to the direct route between origin and destination.DEFINED IN Hub-and-spoke routing
Circumscription: The condition of good land being bounded by unusable terrain, so that the defeated cannot flee and are absorbed instead.DEFINED IN Origin of the state
Citation: A pointer to a source, asserting that a specific document supports a specific claim.DEFINED IN Citation without verification
Citation anchor: A structured reference from a documented claim to the source evidence for it.DEFINED IN Documentation that points at its evidence
Civil-military problematique: Feaver's formulation of the puzzle: the protector must be strong enough to defend and constrained enough not to rule.DEFINED IN Civilian control
Cladding: The outer glass layer of slightly lower index that forms the guiding boundary and keeps it clean.DEFINED IN Guided light
Class invariant: A property of an object that holds before and after every public call, though not necessarily during one.DEFINED IN Design by contract
Class-level shock: An influence common to every pupil in one class in one year, which averaging across pupils cannot reduce.DEFINED IN Value-added ranking instability
Clausius-Clapeyron relation: The equation linking vapour pressure to temperature, giving the near-exponential sensitivity used here.DEFINED IN Pluto's seasonal atmosphere
Clear error: The deferential standard for findings of fact, satisfied only when the reviewing court is left with a definite conviction that a mistake was made.DEFINED IN Appellate deference
Clearing point: The temperature at which thermal motion destroys the orientational order and the material becomes an ordinary isotropic liquid.DEFINED IN Liquid crystals
Client-side and server-side discovery: The caller fetches the instance list and picks one itself, versus sending to a fixed proxy that holds the list on its behalf.DEFINED IN Service discovery
Climacteric fruit: Fruit showing a respiration and ethylene surge at ripening, and able to ripen fully after harvest.DEFINED IN Ripening by contagion
Climacteric ripening: Ripening driven by a self-amplifying burst of ethylene, as in bananas, avocados and tomatoes.DEFINED IN Chilling injury in fruit
Clinker: The fused nodules produced by burning limestone with clay, ground with gypsum to make Portland cement.DEFINED IN Cement hardening
CLOCK: An approximation of least-recently-used using one reference bit per item and a sweeping hand.DEFINED IN Choosing what to forget
Clock bias: The receiver clock's difference from GPS system time.DEFINED IN How does GPS find your location?
Clock skew / drift: The instantaneous difference between two clocks, and the rate at which that difference grows between corrections.DEFINED IN Clock synchronization
Clohessy-Wiltshire equations: The standard linearised description of relative motion near a target in a circular orbit.DEFINED IN Orbital rendezvous
Clonal propagation: Raising a crop from tubers, cuttings or suckers, so the offspring are genetically identical to the parent.DEFINED IN Monoculture fragility
Close-hauled: Sailing as near to the wind direction as the boat can usefully manage.DEFINED IN Sailing upwind
Closed system: A region across whose boundary you track every flow of energy; the argument hereDEFINED IN Cooling a room with a fridge
Closed, open, half-open: The three breaker states: calls flowing and failures counted; calls rejected immediately; a limited trial to test recovery.DEFINED IN Circuit breakers
Closure: The discharge of an active goal, by completion, abandonment, handover, or a concrete plan.DEFINED IN Unfinished tasks
Closure table: A table of every ancestor-descendant pair with its depth, making reachability a plain join.DEFINED IN A tree in a table of rows
Clustering coefficient: The fraction of a node's neighbour pairs that are themselves connected, averaged over the network.DEFINED IN Small-world networks
Co-brand agreement: A contract under which a bank buys miles in bulk from an airline to award to its cardholders.DEFINED IN Frequent-flyer currency
Co-current (parallel) flow: The same two streams running in the same direction, which converge toward a common temperature and so exchange far less.DEFINED IN Countercurrent heat exchange
Co-regulation: An adult lending regulation to a child who cannot yet manage strong feeling alone; the developmental precursor of self-regulation.DEFINED IN Worst behaviour at home
CO-STAR: Context, Objective, Style, Tone, Audience, Response; a widely circulated prompt framework, used here as one example among many.DEFINED IN Twenty-five acronyms, nine pieces
Co-tidal line: A line joining places where high water occurs at the same hour; these radiate from an amphidromic point.DEFINED IN Amphidromic points
Coagulation: The aggregation of denatured protein chains into an insoluble network.DEFINED IN Setting a stain
Coarticulation: The overlap of adjacent speech sounds in the mouth, which erases their boundaries in the signal.DEFINED IN Reading acquisition
Code challenge: The value derived from the verifier and sent on the authorization request, normally its SHA-256 digest under method S256.DEFINED IN Proving you started the exchange you are finishing
Code rot: Decay of a codebase relative to its changing environment; the other, unrelated sense of "software aging".DEFINED IN Software aging
Code verifier: A high-entropy random string generated per authorization request and revealed only at the token endpoint.DEFINED IN Proving you started the exchange you are finishing
Codeword: A full transmitted block, message bits plus check bits, drawn from the agreed legal set.DEFINED IN Error-correcting codes
Codification: The moment a fluid practice is written down as a rule, typically by an outside authority.DEFINED IN Folk craft regionalism
Coefficient of friction: The ratio of resisting force to load between two surfaces; for ice it varies strongly with temperature and speed.DEFINED IN Slippery ice
Coefficient of performance: Heat moved divided by work spent; greater than one, and irrelevantDEFINED IN Cooling a room with a fridge · How does a refrigerator cool food?
Coercion resistance: The stronger property that a voter under observation still cannot be forced to demonstrate compliance.DEFINED IN Secret ballot
Coercive diplomacy: The use of pressure short of war to change another state's behaviour rather than its capacity.DEFINED IN Blockade and resolve
Coevolution: Reciprocal evolutionary change in two lineages, each a selective pressure on the other.DEFINED IN Pollination specificity
Coexistence period: The interval during which old and new systems both serve production traffic.DEFINED IN Choosing the first piece to replace
Coherence time: Roughly r₀ divided by the wind speed aloft; how long the wavefront distortion holds still.DEFINED IN Atmospheric seeing limit
Coherent addition: Summation of waves holding a fixed phase relationship, so amplitudes add and power rises as the square of the count.DEFINED IN Massed string sound
Cohesion: Attraction holding a single material to itself.DEFINED IN Adhesion
Cohesion-tension theory: The account, from Dixon and Joly in the 1890s, in which sap ascends as a continuous column pulled by evaporation and held together by water's cohesion.DEFINED IN Cohesion-tension sap ascent
Cohort marker: An attribute, such as a name, that reliably indicates when its bearer was born and so signals age rather than taste.DEFINED IN Given-name fashions
Coincidental duplication: Code that is identical because two unrelated rules currently produce the same result, rather than because they express one rule.DEFINED IN When removing duplication hurts
Cold ischaemia time: The interval a recovered organ spends chilled and without blood supply before transplantation.DEFINED IN Organ allocation matching
Cold record: The written transcript and exhibits an appeal court works from, lacking the live testimony the trial court observed.DEFINED IN Appellate deference
Cold start: The added latency of a request that must first construct the execution environment and run initialisation.DEFINED IN Cold starts
Collaborative inhibition: The reliable finding that people recalling together produce less than the pooled total of the same people recalling alone.DEFINED IN Shared memory in couples
Collapse (Tainter's sense): A rapid, substantial loss of an established level of complexity.DEFINED IN Societal collapse
Collateral: An asset pledged to the lender, seizable on default, which converts a promise into a claim on property.DEFINED IN Credit
Collective action problem: A situation where each participant's individually rational choice produces an outcome worse for all, with no participant able to fix it alone.DEFINED IN Grade inflation
Collective effervescence: Durkheim's term for the heightened sense of unity generated by coordinated group action.DEFINED IN Ritual meaning
Collective impact case: A situation where an outcome is caused by many acts, none of which individually appears to make a difference.DEFINED IN Imperceptible harms
Colligative property: A property of a solution that depends on the number of dissolved particles, not on what they are; freezing-point depression, boiling-point elevation, and osmotic pressure are the standard examples.DEFINED IN Freezing-point depression
Colour index: Brightness through two filters, subtracted, used as a stand-in for temperature.DEFINED IN Star colors
Column separation: The opening of a vapour cavity when a transient drives pressure down to the fluid's vapour pressure.DEFINED IN Water hammer
Column-level lineage: Lineage tracked per field rather than per table; more precise, harder to derive reliably.DEFINED IN Lineage
Combatant's privilege: Immunity from prosecution for lawful acts of war, forfeited by those who fight without meeting the conditions of combatant status.DEFINED IN Combatant identification
Combinatorial coding: Representing an item by which subset of broadly-tuned detectors it activates, rather than by a dedicated detector.DEFINED IN Smell coding
Command: A message instructing a named recipient to do something, which may be refused.DEFINED IN Commands and events · Separating the read model from the write model
Commander's intent: The statement of purpose, end state and acceptable risk that a subordinate uses to judge what to do when the plan fails.DEFINED IN Mission command
Commensal pathway: Domestication beginning with a wild animal that fed around human settlements and was selected for tolerating people.DEFINED IN Domestication
Commitment: Deliberately removing your own options so that a threat becomes credible.DEFINED IN Escalation · Holding a reserve
Commitment device: An arrangement that makes a promise credible by making its breach costly or impossible.DEFINED IN Constitutional entrenchment · Guaranteed secrecy · Mandated rest days · Mental accounting
Commitment problem: The difficulty of making a threat believable when executing it would harm the threatener.DEFINED IN Deterrence · Peace negotiation
Commodification: The process by which a practice acquires a price and is produced for sale, changing what it is produced for.DEFINED IN Authenticity
Commodity money: Money whose material has value in its own right, such as weighed silver.DEFINED IN Origin of money
Common Crawl: A large, regularly released public archive of crawled web pages, widely used as a training-data source.DEFINED IN Poisoning the well
Common fate: The grouping cue by which elements moving together are taken to belong to one object.DEFINED IN Visual grouping
Common of pasture: A defined right, held by named households, to graze a shared pasture; not open access.DEFINED IN Common high pasture
Common region: The grouping cue by which elements inside a shared enclosure are taken as a set.DEFINED IN Visual grouping
Common value: A value that is the same for every bidder but known to none of them, as opposed to a private value each bidder knows for themselves.DEFINED IN Winner's curse
Common-mode current: Current flowing on the outside of a coaxial cable, which makes the cable itself radiate.DEFINED IN Antenna ground plane
Common-mode failure: A single cause that disables several redundant items at once, defeating the assumption of independence.DEFINED IN Engineered redundancy
Common-pool resource: A resource nobody owns and nobody can easily be excluded from, so restraint by one user benefits the rest.DEFINED IN Fishery collapse · Overtourism
Communication overhead: The effort spent keeping people's understanding of the work aligned, which grows faster than headcount.DEFINED IN Coordination cost
Communitas: The levelled, intensely bonded condition Turner described among people sharing a liminal phase.DEFINED IN Liminality in initiation
Community of practice: The group of practitioners whose shared standards, vocabulary and judgements a learner is joining, not merely learning from.DEFINED IN Learning a trade by standing there
Compaction: Consolidation of young sediment as water is squeezed from its pore spaces and organic matter decays, lowering the surface without removing material.DEFINED IN Delta subsidence · Memory fragmentation · The small files problem
Companionate love: Affection and deep attachment for someone whose life is entwined with one's own.DEFINED IN Fading attraction
Comparability: The property that lets performances from different eras sit in one series; broken by a change that shifts the baseline for everyone.DEFINED IN Equipment bans in sport
Compare-and-swap: An atomic instruction that writes only if the current value matches an expected one, used to detect lost updates.DEFINED IN Immutability · Transactions on immutable storage
Comparison good: A purchase a buyer wants to inspect against alternatives before committing, as opposed to a convenience good.DEFINED IN Retail clustering
Comparison lower bound: The log2 of n factorial floor, roughly n log n, on comparisons needed to sort.DEFINED IN Half-sorted is enough
Comparison sort: A sorting method whose only access to the data is pairwise ordering queries.DEFINED IN The sorting floor
Compartmentation: The separation of reactive substances into different cell compartments, so a reaction only runs when the barrier is breached.DEFINED IN Chilling injury in fruit
Compatibilism: The view that free will requires freedom from coercion and compulsion, not freedom from causation.DEFINED IN Free will
Compensating action: An operation that offsets the effects of something already done, used where rejection is impossible.DEFINED IN Commands and events
Compensating differential: The extra pay a labour market attaches to a job with worse conditions, in order to keep it staffed.DEFINED IN Teacher attrition in hard schools
Compensating event: A later event that corrects an earlier one, since events are never edited.DEFINED IN Event sourcing
Compensation: An action that undoes an already-completed step when a later step fails, since a distributed process cannot simply roll back.DEFINED IN Choreography versus orchestration · Translation equivalence
Compensatory growth: Restoration of an organ's mass by growth of the remaining tissue, without rebuilding the removed part.DEFINED IN Limits of regeneration
Competing objectives: The failure mode where helpfulness, instruction-following or role coherence is set against refusal.DEFINED IN Talked out of its own rules
Competitive exclusion: The elimination of weaker competitors by a dominant that monopolises a limiting resource, here light.DEFINED IN Grazing and grassland richness · Keystone species · Pasteurised mushroom substrate
Competitive release: Expansion into niches left vacant by species absent from the island.DEFINED IN Island size rule
Complement rule: Computing the chance of "at least one" by finding the chance of "none" and subtracting from 1.DEFINED IN Birthday problem
Complementarity: Capture of a resource in a place or at a time the other component was not using it.DEFINED IN Agroforestry overyielding
Complete (of a theory): Proving or refuting every sentence in its language; distinct from Gödel's completeness theorem about first-order logic.DEFINED IN Incompleteness
Complete-case analysis: Discarding every record with any missing value; also called listwise deletion.DEFINED IN Dropping incomplete records
Compliance: Public agreement without private change, the characteristic product of majority pressure.DEFINED IN Minority influence
Composite index: An index over several columns in order; only its leading columns are independently useful.DEFINED IN Indexing
Composition in performance: Building the song afresh during the singing, rather than reciting a memorised text.DEFINED IN Formulaic oral composition · Oral tradition
Composition over inheritance: Building behaviour by assembling collaborating objects at run time rather than by fixing it in a class hierarchy.DEFINED IN Wrapping without changing
Composition root: The single place where an application wires its objects together and decides their lifetimes.DEFINED IN The singleton regret
Compounding: Adding earned interest back to the principal so it, too, earns interest.DEFINED IN Compound interest
Compounding reliability: The multiplication of per-step success rates across a chain, which falls quickly as steps are added.DEFINED IN Many agents, one task
Compression: The process of moving later flights forward into slots released by cancellations.DEFINED IN Ground delay programs
Compressive asphyxia: Death from external pressure on the chest that prevents the lungs from expanding; the usual cause of death in crowd disasters.DEFINED IN Crowd crush
Computational irreducibility: A system's future cannot be obtained faster than by simulating it step by step.DEFINED IN Cellular automata
Concealed work: Any part of an installation that the finished building makes inaccessible without destructive opening-up.DEFINED IN Rough-in inspection
Concentrated benefits, diffuse costs: The pattern in which a policy's few large beneficiaries organise to defend it while its many small losers do not organise to end it.DEFINED IN Persistent rules · Regulatory capture
Concentration of distances: The tendency for all pairwise distances to become nearly equal as dimension grows.DEFINED IN Curse of dimensionality
Concept drift: The relationship between input and outcome itself changes, so previously correct labels become wrong.DEFINED IN Model drift
Concept inventory: A multiple-choice instrument whose wrong options are the known misconceptions, so scores reveal the model rather than the vocabulary.DEFINED IN Classroom misconceptions
Conceptual change: The restructuring of an existing explanatory model, as opposed to adding new facts alongside it.DEFINED IN Classroom misconceptions
Conceptual metaphor: A systematic correspondence between a concrete source domain and an abstract target domain, of which everyday expressions are the surface trace.DEFINED IN Metaphor
Conceptual model: Entities and relationships in business language, with no keys, attributes, or technology.DEFINED IN Drawing the same model three times
Concurrent events: A pair with no happens-before relation in either direction; unordered rather than of unknown order.DEFINED IN Clock synchronization
Condensation drying: A dishwasher cycle with no heater or fan at the end, relying on residual heat in the load and a cool tub wall for the vapour to condense on.DEFINED IN Dishwasher drying
Condenser: The coils where the refrigerant gives up its heat, and the half of the machine anDEFINED IN Cooling a room with a fridge · How does a refrigerator cool food?
Condition number: How much a problem amplifies relative error in its inputs; for a − b it is (|a| + |b|) / |a − b|.DEFINED IN Catastrophic cancellation
Condition-based maintenance: Replacing on a measured symptom of impending failure rather than on elapsed time or cycles.DEFINED IN Preventive replacement
Conditional cooperation: The observed disposition to contribute in proportion to what others are believed to be contributing.DEFINED IN Compulsory taxation
Conditional independence: The condition, required for likelihood ratios to multiply, that the reasons any one report might be wrong are unrelated to the reasons any other might be.DEFINED IN Strategic deception
Conditionality: The terms a grant carries, from accounting requirements to substantive policy demands.DEFINED IN Conditional spending grants
Conditioned tolerance: A compensatory response elicited in advance by cues that reliably precede the drug.DEFINED IN Drug tolerance
Conditioning: The fact that a model's output distribution depends on the entire preceding context, so any added text shifts what follows.DEFINED IN A calibrated role · Monty Hall problem · Placebo effect
Conditioning film: The organic residue coating a wet surface first, providing the anchorage cells attach to.DEFINED IN Washing machine odour
Conditioning on winning: Revising your estimate downward in advance to reflect what it would mean that every rival bid less.DEFINED IN Winner's curse
Condorcet winner: A candidate who would beat every other in a one-on-one majority contest; may not exist.DEFINED IN Voting rules
Conductivity test: A vigour test measuring electrolytes leaking from imbibing seed, reading membrane damage directly.DEFINED IN Seed vigour versus germination
Conductor bundle: Two or more spaced sub-conductors used as one phase, raising the effective diameter to suppress corona.DEFINED IN High-voltage transmission
Conduit: A dissolution-widened fracture large enough to carry turbulent flow rather than seepage.DEFINED IN Sinking streams in karst
Cone cells: The eye's three colour receptors, whose combined response, not the dominant wavelength, sets the colour perceived.DEFINED IN Why is the sky blue?
Confirmation prompt: The approval asked for before an operation runs, whose usefulness depends on how precisely that operation can be named.DEFINED IN Tool granularity
Conflict markers: The delimiters a tool writes into a file to present both competing versions of a region for a human to resolve.DEFINED IN Merge conflicts
Conflict-free replicated data type: A data structure whose concurrent updates commute, so replicas converge without coordination.DEFINED IN The CAP theorem
Conformal: A projection preserving angles and local shapes, at the cost of varying scale.DEFINED IN Map projection distortion
Conformation: One of the many shapes a flexible chain molecule can take by rotation about its bonds, without breaking any of them.DEFINED IN Rubber elasticity
Conformed layer: The stage where shared meaning is applied once: deduplication, typing, and agreed definitions of an entity.DEFINED IN Refinement stages
Conformist transmission: A learner's bias toward whichever variant is most common among the models available.DEFINED IN Folk craft regionalism
Confounded identification: The situation where two explanations imply the same observable pattern, so no amount of that data decides between them.DEFINED IN Divorce contagion
Confounder: A variable influencing both the treatment received and the outcome; conditioning on it is what makes the subgroup comparison the right one.DEFINED IN Simpson's paradox
Confounding: A variable influencing both who gets the treatment and how they fare, making the raw comparison unreadable.DEFINED IN Randomized trials
Confused deputy: A privileged component induced to use its authority on behalf of a party that lacked it.DEFINED IN A valid token in the wrong place
Congestion externality: The cost each additional user imposes on all the others, which does not appear in that user's own decision.DEFINED IN Overtourism
Conjugate action: Tooth flank geometry that holds the angular velocity ratio constant throughout the engagement.DEFINED IN Involute gear teeth
Connascence: A taxonomy ranking forms of dependency (on name, position, meaning, timing, order) by how strongly they bind two components.DEFINED IN Coupling
Connection pool: Pre-opened database connections held by one instance and reused across requests.DEFINED IN Connection exhaustion before CPU
Connotation: The associations a word carries beyond its literal reference, accumulated from the contexts it has been used in.DEFINED IN Euphemism
Consent: The host state's agreement to a mission's presence, which is usually revocable and can be narrowed short of expulsion.DEFINED IN Peacekeeping mandates
Consequence argument: Van Inwagen's argument that since we control neither the past nor the laws, we control nothing they entail.DEFINED IN Free will
Consistency: Holding the same position across occasions without hedging or drift; the variable that carries minority influence.DEFINED IN Minority influence
Consistent hashing: Placing keys and servers in one circular hash space, each key owned by the first server clockwise; introduced in 1997 by Karger and colleagues.DEFINED IN Adding a machine without moving the data
Consolidation: Combining several small shipments into one full vehicle load to cut cost per unit moved.DEFINED IN Cross-docking · Memory reconstruction · Sleeping on a problem
Conspecific negative density dependence: The tendency of a species' local abundance to depress its own recruitment, giving rare species an advantage.DEFINED IN Janzen-Connell seedling mortality
Conspicuous consumption: Veblen's term for spending whose purpose is visible display of ability to spend rather than use.DEFINED IN Conspicuous display
Constant-time comparison: Byte comparison that always takes the same time, so timing reveals nothing about a mismatch.DEFINED IN A notification you did not ask for
Constituent order: The conventional sequence of subject, verb and object in a language's basic clause.DEFINED IN Word order
Constitutive aim of belief: The idea that a state counts as a belief only insofar as it is regulated by whether the proposition is true.DEFINED IN Believing at will
Constitutive rule: A rule that defines what the activity is rather than merely restraining it.DEFINED IN Equipment bans in sport · Promising
Construct: The unobservable attribute a test is meant to be evidence about, such as reading comprehension.DEFINED IN Test validity
Construct under-representation: The test samples only part of the construct, so genuine strength outside that part goes unscored.DEFINED IN Test validity
Construct validity: Whether a test actually measures the capability it is taken to measure, as opposed to something correlated with it.DEFINED IN Benchmark saturation
Construct-irrelevant variance: Score differences caused by something other than the construct, such as reading load on a mathematics paper.DEFINED IN Test validity
Consumer group: A set of consumers that divide a topic's partitions between them, each partition going to exactly one member.DEFINED IN Why adding a worker stops the others
Consumer price index: The cost of a fixed representative basket, from which the headline rate is calculated.DEFINED IN What is inflation?
Consumer surplus: The difference between what a buyer would have been willing to pay and what they actually paid.DEFINED IN Paradox of value
Consumer-driven contract: Expectations recorded by each consumer and verified against the provider.DEFINED IN Agreeing the shape before the substance
Consumer-driven contract test: A test written from a consumer's expectations and run in the producer's pipeline, so a breaking change fails before release.DEFINED IN The distributed monolith
Contact temperature: The temperature the interface settles at when two bodies touch, weighted by their effusivities.DEFINED IN Thermal conductivity of touch
Container: A normal operating-system process confined by namespaces and control groups, sharing the host kernel.DEFINED IN Isolates, containers, and startup cost
Contamination: Benchmark items appearing in a model's training data, turning a test of ability into a test of recall.DEFINED IN Benchmark saturation
Contemporaneity problem: The difficulty of establishing how many recorded buildings were occupied simultaneously, given dating no finer than a ceramic phase.DEFINED IN Ancient population estimates
Content addressing: Naming stored data by the hash of the data itself, which lets identical layers be stored and transferred once.DEFINED IN Layers are diffs · Tags versus digests
Context assembly: Selecting and arranging what goes into a prompt, including retrieved material.DEFINED IN Orchestration
Context propagation: Passing the trace and span identifiers across a service boundary, usually in a header or message metadata.DEFINED IN Distributed tracing
Context reinstatement: Returning to the surroundings in which something was learned in order to recall it, which is the account the return-to-the-room result argues against here.DEFINED IN Doorway effect
Context relevance: What proportion of the retrieved context was useful, which catches answers buried among distractors.DEFINED IN Evaluating retrieval separately
Context window: The maximum number of tokens a model can take in one request, covering system prompt, transcript, attachments, and the generated reply.DEFINED IN Context window · Many agents, one task · System prompt priority
Contextual encoding: Escaping a value for the grammar it is about to enter, rather than filtering once at the source.DEFINED IN Output as untrusted input
Contextual retrieval: Prepending a short description of a chunk's place in its document before embedding or indexing it, so the chunk is interpretable on its own.DEFINED IN Chunking
Continence: The state of having wrong desires and mastering them, ranked below virtue.DEFINED IN Effortless virtue
Continental axis: The dominant orientation of a landmass, east-west for Eurasia and north-south for Africa and the Americas.DEFINED IN East-west diffusion
Continentality: The tendency of interiors to greater sunshine, drier air and wider temperature swings than maritime margins.DEFINED IN Mass elevation effect
Contingency: The dependence of an outcome on the subject's action; the quantity the prefrontal detector is thought to track.DEFINED IN Learned helplessness · Overheard speech and vocabulary · Sibling regression
Contingency fuel: A planned allowance above trip fuel, covering ordinary deviations such as routing changes and unforecast winds.DEFINED IN Contingency fuel
Continued influence effect: The tendency for retracted information to keep affecting reasoning even in people who correctly recall the retraction.DEFINED IN Persistence of misinformation
Continuous Access Evaluation Profile (CAEP): A Shared Signals profile for pushing events such as session-revoked to relying parties so they can act before a token expires.DEFINED IN Signing out everywhere
Continuous batching: Admitting and retiring sequences between individual decode steps, removing most of the waiting that static batching imposes.DEFINED IN Batching and the throughput trade · Prefill and decode
Continuous integration: The practice of every developer merging into the shared mainline at least daily and verifying the merged result, not merely a build server.DEFINED IN Merging often
Contour scaling: Loss of a sheet parallel to the dressed face, typical of face-bedded work.DEFINED IN Natural bed in stone
Contract test: An automated check that a running implementation still conforms to the agreed specification.DEFINED IN Agreeing the shape before the substance · The test pyramid
Contract-first (design-first): Agreeing a machine-readable interface specification before implementing either side.DEFINED IN Agreeing the shape before the substance
Contraction: Keeping the first and last letters, dropping the middle, usually under an overline.DEFINED IN Scribal abbreviation
Contrast effect: The shift in a script's mark caused by the standard set by the immediately preceding script.DEFINED IN Marker disagreement
Contrastive training: Learning by pulling matching pairs together in the space while pushing non-matching pairs apart.DEFINED IN Embedding space · Multimodal fusion
Contrastive underdetermination: The claim that rivals agreeing on all evidence exist for a given theory.DEFINED IN Underdetermination of theory
Control group: A comparison group selected the same way, so that regression affects it equally and cancels out of the comparison.DEFINED IN Regression to the mean
Control group (cgroup): A kernel facility that meters and limits the CPU, memory, and I/O a group of processes may consume.DEFINED IN Isolation without a machine
Control lag: The delay between a control action and its effect appearing in the measured signal.DEFINED IN Scaling that overshoots
Control plane: The path that changes that configuration: registration, deployment, scaling, health-driven membership changes.DEFINED IN Control plane and data plane
Control principle: The claim that people are morally assessable only for what lies within their control.DEFINED IN Moral luck
Controlled departure time: The take-off time computed backwards from a flight's assigned arrival slot.DEFINED IN Ground delay programs
Convective zone: The outer region where energy is carried instead by rising and sinking gas.DEFINED IN Photon escape time
Convention: A shared regularity that lets one learned fact apply to many cases; every exception reduces its value for the whole set.DEFINED IN Least astonishment
Conventional radiocarbon age: Computed from the measured ratio using the Libby half-life of 5568 years, by convention rather than best estimate.DEFINED IN Radiocarbon calibration plateaus
Convergence: The growth in similarity between partners over the course of a relationship, distinct from similarity present at the start.DEFINED IN Similar partners
Convergence-projection: The account in which visceral and somatic afferents synapse on shared spinal neurons, so the brain cannot distinguish their origin.DEFINED IN Referred pain
Convergent evolution: Independent lineages arriving at similar traits under similar selective pressures.DEFINED IN Convergent evolution
Conversion: Private, often delayed change in belief, as distinct from public agreement.DEFINED IN Minority influence
Cookie tossing: Setting a cookie for a parent domain from a subdomain the attacker controls, exploiting the lack of cookie integrity.DEFINED IN Logged into someone else's account
Cooldown / stabilisation window: An enforced pause after a scaling action, during which further actions are suppressed or damped.DEFINED IN Scaling that overshoots
Cooperative incremental rebalancing: KIP-429's protocol, in which only reassigned partitions are revoked, over two rounds.DEFINED IN Why adding a worker stops the others
Cooperative termination: Participants querying each other for the decision when the coordinator is unreachable.DEFINED IN The blocking commit
Coordinated airport: One where demand exceeds capacity, so access must be allocated in advance rather than requested on the day.DEFINED IN Airport slot grandfathering
Coordination equilibrium: An arrangement everyone follows because everyone else does, which nobody can improve on by moving alone.DEFINED IN Spelling reform · Tipping customs
Coordination loss: Output lost because combined efforts are imperfectly timed or aligned, with no reduction in willingness.DEFINED IN Social loafing
Coordination point: A date whose value comes from everyone expecting everyone else to use it, so it becomes self-reinforcing.DEFINED IN Festival calendars
Coordination problem: A situation in which each actor's best move depends on what the others do, so that shared expectation decides the outcome.DEFINED IN Civilian control · Concert pitch standard
Coreference: Working out which earlier expression a pronoun or referring phrase points to.DEFINED IN Attention as a budget
Coriolis deflection: The apparent turning of moving air caused by the Earth's rotation, which makes cross-equatorial inflow a southwesterly.DEFINED IN Monsoon
Coriolis effect: The apparent deflection of moving air on a rotating planet, to the right in the northern hemisphere.DEFINED IN Asymmetric flight times
Coriolis force: The apparent sideways force arising from describing motion in the Earth's rotating frame, proportional to speed and zero at the equator.DEFINED IN Geostrophic wind
CORNEA: Wykstra's condition restricting when "I see no reason" licenses "there is no reason".DEFINED IN Problem of evil
Corner solution: An optimum on the boundary, where the first-order condition holds as an inequality rather than an equality.DEFINED IN Corner solutions
Corona discharge: Ionisation of air at a conductor's surface when the local electric field is too strong, wasting power and causing radio noise.DEFINED IN High-voltage transmission
Correction line: A periodic reset of the rectangular grid to absorb the convergence of meridians.DEFINED IN Cadastral survey patterns
Correlated error: A mistake shared by every sample, which voting cannot detect because the samples agree.DEFINED IN Self-consistency
Correlated risk: Risks driven by a shared cause, so they occur together and defeat the averaging that pooling relies on.DEFINED IN Insurance pooling
Correlation coefficient (r): The factor by which a standardised score is expected to shrink from one measurement to the next.DEFINED IN Regression to the mean
Correspondence bias: Inferring a matching disposition from behaviour even when the situation sufficiently explains it; the more careful name for the fundamental attribution error.DEFINED IN Attribution asymmetry
Correspondence problem: Which element in one frame is the same as in the next; wrong answers produce apparent reversal.DEFINED IN Aliasing
Corroboration: Popper's term for a theory's record of surviving serious attempts at refutation, explicitly not a measure of future reliability.DEFINED IN Problem of induction
Corrosion inhibitor: A species that renders exposed metal unreactive, typically by forming or restoring a passive film.DEFINED IN Self-healing coatings
Cosine distance: The usual measure of how far apart two embeddings are, and the signal the correction loop follows.DEFINED IN What a list of numbers remembers
Cosine similarity: The usual measure of nearness between two embeddings, based on the angle between them.DEFINED IN Caching an answer nobody asked for exactly · Embedding space
Cosmic microwave background: The all-sky remnant glow of the hot early universe, now observed at about 2.7 kelvin.DEFINED IN Dark night sky
Cost disease: The tendency of sectors with little productivity growth to become relatively more expensive as productivity rises elsewhere in the economy.DEFINED IN Cost disease · Repair economics
Cost imposition: Attacking to make the opponent's policy expensive rather than to destroy its forces.DEFINED IN Asymmetric warfare
Cost of carriage: The fraction of any additional fuel load consumed simply in flying that load, roughly proportional to time aloft.DEFINED IN Contingency fuel
Cost tiering: Offering several capability and price levels and assigning work across them.DEFINED IN Model routing
Cost-plus (day rate): Payment for hours and materials as incurred, with the customer carrying the variance.DEFINED IN Quoting a job
Cost-push inflation: Prices rising because inputs became costlier, usually alongside falling output.DEFINED IN What is inflation?
Costly signal: A display kept honest by an expense only a genuine sender can bear.DEFINED IN Blushing · Costly religious demands · Design restraint · Family estrangement · Trust asymmetry · Uninformative advertising
Costly signalling: The general condition that a claim about an unobservable quality is credible only when cheaper for genuine holders to make.DEFINED IN Conspicuous display · Ritual meaning · Sharing under scarcity
Coulomb damping: Energy loss by dry sliding friction, in which loss per cycle scales with amplitude rather than amplitude squared.DEFINED IN Cracked bell tone
Countable additivity: The axiom that the probability of a countable union of disjoint events equals the sum of their probabilities.DEFINED IN Fair lottery over the integers
Counter-battery fire: Fire directed at the enemy's artillery rather than at his manoeuvre forces.DEFINED IN Shoot-and-scoot artillery
Counter-enclave: A parcel of the surrounding state lying inside an enclave.DEFINED IN Enclaves
Counter-majoritarian difficulty: Bickel's name for the tension between unelected review and majority rule.DEFINED IN Judicial review
Countercurrent exchange: Two flows running in opposite directions in thermal or chemical contact, so a small gradient is maintained along the whole length instead of being spent at one point.DEFINED IN Countercurrent heat exchange
Counterexample: An argument of the same form with true premises and a false conclusion, which isDEFINED IN What makes an argument logically valid?
Countermeasure: Any measure, technical or behavioural, that spoils one necessary step in a weapon's chain of effect.DEFINED IN Fading advantage of a new weapon
Countersignalling: The high type's abstention from display, effective only where the audience already knows their standing.DEFINED IN Conspicuous display
Counterurbanisation: Net movement of population from cities to smaller settlements, often within commuting range.DEFINED IN Rural depopulation
Coup-proofing: Structural measures such as parallel forces and divided command that keep plotters from combining.DEFINED IN Civilian control
Coupled oscillators: Two vibrating systems joined so that energy passes between them, splitting a shared frequency into two and producing an exchange.DEFINED IN Cello wolf tone
Coupling: The degree to which one unit of code depends on assumptions about another; measured by what must change together, not by shared text.DEFINED IN Coupling · Technical debt · Testability as a design property · The middleman that reduces connections
Coupon collector's problem: The classical name for this question: how many uniform random draws are needed to see all n items.DEFINED IN Completing a collection
Covalent network: A solid in which bonding extends continuously through the whole crystal, as in diamond.DEFINED IN Carbon allotropes
Covariate shift: The distribution of inputs changes while the relationship between input and outcome holds.DEFINED IN Model drift
Cover: The depth of concrete between a reinforcing bar and the surface, setting how long the bar stays protected.DEFINED IN Reinforced concrete
Cover story: A manufactured alternative explanation for how a target was found, allowing sensitive intelligence to be acted on safely.DEFINED IN Unusable intelligence
Coverage instrumentation: Recording which code paths actually executed during a period of observation.DEFINED IN Code that never runs, and code that runs once a year
Coverage ledger: A record of what was examined, by what method, and with what outcome, including failures.DEFINED IN Writing down what you could not determine
Covering force: The force held ready to meet an enemy squadron if it sorties, sized by that possibility rather than by any current activity.DEFINED IN Fleet in being
cPRA: Calculated panel reactive antibody: the percentage of the donor pool a candidate has antibodies against, and so cannot receive from.DEFINED IN Organ allocation matching
CQRS: Command query responsibility segregation: separate models for changing state and for reading it.DEFINED IN Separating the read model from the write model
Cracking: Dividing opposing voters across many districts so they are a minority in each.DEFINED IN District boundaries
Craquelure: The network of fine cracks in aged paint and varnish, whose pattern follows the support and ground beneath.DEFINED IN Patina and age value
Crash blossom: A headline made ambiguous by its own compression, named after a 2009 example about a violinist and a plane crash.DEFINED IN Headlinese
Crash-only software: A design in which stopping is always a crash and starting is always recovery, so the recovery path is continuously exercised.DEFINED IN Failing fast
CRDT: A data type whose merge operation is commutative, associative and idempotent, so replicas converge regardless of the order updates arrive in.DEFINED IN Eventual consistency
Credence good: One whose quality the buyer cannot judge even after purchase and use.DEFINED IN Brand advertising · Occupational licensing · Paying for the five-minute fix
Credibility: The adversary's estimate that a threat would actually be carried out, distinct from the ability to carry it out.DEFINED IN Deterrence
Credibility weighting: Blending an individual's claims experience with the class average, weighted by how much individual data exists.DEFINED IN Experience rating
Credibility-enhancing display: Henrich's term for a costly act that makes an onlooker take the actor's stated belief to be sincere.DEFINED IN Costly religious demands
Credible commitment: A promise made believable by arranging that breaking it would be costly to the promiser.DEFINED IN Hostage capital
Credit bureau: An institution that records borrowers' repayment histories, making a local reputation portable between lenders.DEFINED IN Credit
Creep: Slow permanent deformation of a solid under sustained stress, without melting or fracture.DEFINED IN Glacier flow
Crest factor: The ratio of a signal's peak level to its root-mean-square level.DEFINED IN Broadcast loudness
Crevice corrosion: Attack in an oxygen-starved gap where the passive film cannot be maintained.DEFINED IN Passivation
Crimp: The waviness a yarn takes as it passes over and under its crossmates, supplying a little give before the fibre itself is loaded.DEFINED IN Bias-cut cloth
Criterion: How much evidence a system demands before declaring the signal present; shiftable, and independent of sensitivity.DEFINED IN Pareidolia
Critical angle: The incidence angle, measured from the perpendicular, beyond which no light is transmitted out of the denser medium.DEFINED IN Guided light
Critical charge: The charge that must be deposited on a circuit node to flip its logical state, roughly capacitance times supply voltage.DEFINED IN Radiation-hardened spacecraft computers
Critical closure time: The round-trip time 2L over c, below which a closure produces the full Joukowsky surge.DEFINED IN Water hammer
Critical coagulation concentration: The salt concentration at which the barrier effectively disappears and aggregation becomes fast.DEFINED IN Colloid flocculation
Critical density: The vehicle spacing above which uniform flow stops being stable and small perturbations amplify.DEFINED IN Phantom traffic jams
Critical fabulation: A contested method that narrates archival gaps as explicitly marked speculation.DEFINED IN Historical silence
Critical frequency: The plasma frequency of the densest ionospheric layer overhead, measured routinely by ionosondes.DEFINED IN Low-frequency radio cutoff
Critical path: The longest chain of genuine dependencies, which sets the minimum achievable window.DEFINED IN Recovering a schedule nobody wrote down
Critical power or critical speed: The highest intensity at which the body's internal state can remain steady, and so be sustained for a long time.DEFINED IN Even pacing
Critical radius: The embryo size above which further growth lowers total free energy and so becomes self-sustaining.DEFINED IN Supercooling
Critical trial: In Asch's design, a trial on which the confederates deliberately gave a wrong answer.DEFINED IN Conformity
Critical user journey: An end-to-end sequence a user performs to get value from the service, used as the unit for choosing indicators.DEFINED IN Choosing an indicator
Critical value: The threshold a result is compared against.DEFINED IN Detection limits
Cross cousin: The child of a parent's opposite-sex sibling: mother's brother's or father's sister's child.DEFINED IN Cross-cousin marriage · Merged kinship terms
Cross dowel: A peg set across the grain into which a screw is threaded, so the fastening load is carried by fibres crossing the screw.DEFINED IN Screws in end grain
Cross versus parallel cousin: Children of opposite-sex siblings versus same-sex siblings; identical in relatedness, treated very differently by many marriage rules.DEFINED IN Marrying outside the group
Cross-cutting concern: A requirement that applies across many components and cannot be cleanly localised in any one of them.DEFINED IN Moving failure handling out of the program
Cross-docking: Receiving goods and dispatching them within hours by sorting between vehicles rather than placing them into storage.DEFINED IN Cross-docking
Cross-education: The strength gain observed in an untrained limb after the opposite limb is trained.DEFINED IN Early strength gains
Cross-encoder: A model that takes query and document as a single joint input and emits one relevance score; accurate but not precomputable.DEFINED IN Two-stage retrieval
Cross-entropy loss: The training score that penalizes the model in proportion to how little probability it gave the token that really came next.DEFINED IN Next-token prediction
Cross-infection: Transmission of an organism from one patient to another via an intermediary, most often hands.DEFINED IN Hand hygiene compliance
Cross-link: A chemical bridge tying one chain to another; vulcanisation introduces sulfur cross-links to make raw latex elastic rather than fluid.DEFINED IN Rubber elasticity
Cross-match: Testing a recipient's plasma directly against the specific unit to be given.DEFINED IN Blood compatibility
Cross-modal correspondence: A consistent mapping between properties in different senses, such as rounded shapes with sweetness.DEFINED IN Typeface voice
Cross-reference: The stored mapping from a mastered entity to each source system's own key, which makes a link traceable and reversible.DEFINED IN Which record is the real one
Cross-section: The effective target area for a given interaction; for neutrinos at MeV energies, of order 10⁻⁴⁴ cm².DEFINED IN Neutrino detection
Cross-side network effect: The benefit one group of a platform's users gets from the number of the other group present.DEFINED IN Two-sided market launch
Cross-site request forgery: An attack that abuses ambient cookies to make a request happen, without ever needing to read the reply, and therefore untouched by CORS.DEFINED IN CORS in the web · Requests you did not make
Crossdating: Matching ring-width patterns between samples to give each ring an exact calendar year.DEFINED IN Tree-ring evidence
Crosshatch honing: The fine groove pattern machined into a liner to retain oil and bed the rings.DEFINED IN Light-load diesel running
Crossmatch: A final laboratory test of the specific recipient's serum against the specific donor's cells before the operation proceeds.DEFINED IN Organ allocation matching
Crossmodal perception: The influence of one sense on another, as when background sound alters perceived sweetness.DEFINED IN Inflight taste
Crowd turbulence: Dense crowd motion in which people are displaced unpredictably by transmitted forces rather than by their own movement.DEFINED IN Crowd crush
Crowding: The impairment of letter identification caused by neighbouring letters, strongest away from the fixation point.DEFINED IN Legibility
Cryptographic erase: Rendering data unreadable by destroying the encryption key rather than the data itself.DEFINED IN File deletion
CSPRNG: A cryptographically secure pseudorandom number generator, built so past output does not reveal future output.DEFINED IN Pseudorandomness
Cued retrieval: Distress triggered by encountering a reminder, rather than arising on a fixed internal schedule.DEFINED IN Grief timing
Culminating point: The moment an advance can no longer sustain itself, the same limit read from the campaign's side.DEFINED IN Holding conquered ground · Military logistics
Culminating point of the attack: The moment when an advancing force's strength has decayed to the point where it is weaker than the defender it faces.DEFINED IN Defender's advantage
Cultural capital: Bourdieu's term for knowledge and taste that confer standing and cannot simply be purchased.DEFINED IN Conspicuous display
Cultural capture: Adoption of the regulated industry's assumptions and standards of reasonableness, without any exchange of value.DEFINED IN Regulatory capture
Cultural drift: Change in the frequency of variants caused by the randomness of who copies whom, rather than by any advantage.DEFINED IN Folk craft regionalism
Cultural life script: A culture's shared timetable of expected life events, used as a search plan when recalling one's own past.DEFINED IN Reminiscence bump
Cumulative advantage: The tendency for an early lead to generate the conditions for a larger lead, independently of merit.DEFINED IN Canon formation
Cumulative culture: The accumulation of improvements across generations, possible only when transmission is faithful enough that gains are not lost between them.DEFINED IN Technology loss
Cumulative output: Total units ever produced, as distinct from units produced per period.DEFINED IN Experience-curve pricing
Cupping: Curvature across a panel's width, from unequal movement between its two faces.DEFINED IN Balanced veneer
Curing: The long, cool final stage in which slower compounds such as lignin are broken down and the material stabilises.DEFINED IN Compost heat
Current flag: A redundant marker identifying the version with an open end date, kept for query simplicity.DEFINED IN Recording a change without losing the present
Curse of dimensionality: The collapse of distance contrast and of partitioning strategies as dimension rises.DEFINED IN Approximate nearest neighbour search
Curse of knowledge: The inability to set aside what you know when predicting the judgements or difficulties of someone who does not know it.DEFINED IN Curse of knowledge in teaching · Trade jargon
Cut bank: The eroding outer bank of a meander.DEFINED IN River meanders
Cut score: The point on a score scale at or above which a candidate passes.DEFINED IN Cut scores on licensing exams
Cut vertex: A node whose removal disconnects the network, so no alternative path exists around it.DEFINED IN Just-in-time fragility
Cutoff date: The administrative boundary defining an age group, and the thing the birthday skew actually tracks.DEFINED IN Relative age effect
Cyanoacrylate: The monomer family used in instant adhesives, with a nitrile and an ester group on one carbon of a double bond.DEFINED IN Instant glue
Cyanogenic glucoside: A sugar-bound compound releasing hydrogen cyanide only after enzymatic breakdown; linamarin is cassava's principal one.DEFINED IN Cassava processing
Cyanogenic glycoside: A stable compound, such as amygdalin, that releases cyanide only when tissue damage lets it meet the enzyme stored apart from it.DEFINED IN Sweet fruit, guarded seed
Cycle ageing: Degradation driven by charge and discharge themselves, largely mechanical inDEFINED IN Battery ageing
Cycle service level: The proportion of replenishment cycles expected to pass without a stockout.DEFINED IN Safety stock
Cycle stock: Inventory covering expected demand between replenishments; set by order frequency, not risk appetite.DEFINED IN Safety stock
Cyclic majority (Condorcet's paradox): Majority preference running A over B, B over C and C over A; no Condorcet winner, meaning no option beating every other one-on-one, then exists.DEFINED IN Cyclic majorities
Cyclic re-entry: The return of selected light-zone cells to the dark zone for another round of mutation.DEFINED IN Antibody affinity maturation
Cyclic result: Outcomes in which A beat B, B beat C and C beat A, admitting no consistent ordering.DEFINED IN Group-stage tiebreaks
Cytochrome c: A mitochondrial protein whose release into the cell body assembles the platform that activates caspases.DEFINED IN Programmed cell death
Cytotoxic: A drug that kills cells by damaging DNA or the apparatus of cell division, without recognising cell type.DEFINED IN Chemotherapy selectivity

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D layer: The lowest ionospheric layer, strongly absorbing at medium frequencies by day and largely absent at night.DEFINED IN Radio diffraction
Damage control surgery: A deliberately abbreviated operation that halts bleeding and contamination, deferring repair until physiology is restored.DEFINED IN Casualty evacuation
Damping: Any process that removes energy from an oscillation, such as internal friction, air resistance, or a purpose-built damper.DEFINED IN Resonance
Damping ratio: The fraction of critical damping in a structure, governing how fast free vibration dies away.DEFINED IN Building sway
DAMPs: Damage-associated molecular patterns: molecules released by dying host cells that the immune system reads much as it reads bacterial signals.DEFINED IN Sepsis
Danelaw: The region of England under Scandinavian law and settlement from the late ninth century.DEFINED IN Place names
Danger zone: The temperature bracket, roughly 5 to 63 °C in UK practice, within which food-poisoning bacteria grow at rates that matter over a service period.DEFINED IN Buffet holding time · Leftover spoilage
Dark adaptation: The eye's gradual gain in sensitivity in low light, which makes fifty-lux galleries usable after a few minutes.DEFINED IN Museum lighting
Dark current: Charge accumulating in a sensor without light; the limit on long digital exposures.DEFINED IN Reciprocity failure
Data certification: Marking a dataset as approved for general use; meaningful only when the mark is tied to conditions that are re-checked.DEFINED IN Grade earned, not declared
Data classification: Assigning a dataset to a level in a small vocabulary reflecting the harm its disclosure would cause.DEFINED IN Labelling before deciding
Data contract: An explicit, machine-checkable agreement between a data producer and its consumers covering schema, semantics and service expectations.DEFINED IN Data contracts
Data custodian: The technical holder responsible for storage, protection, availability, and implementing access decisions.DEFINED IN Three kinds of responsible person
Data dependency: An ordering forced because one job consumes what another produces.DEFINED IN Recovering a schedule nobody wrote down
Data gravity: The tendency of accumulated data to hold the systems that use it in place beside it.DEFINED IN The price of being able to leave
Data leakage: Using information unavailable at the moment being predicted.DEFINED IN Point-in-time joins
Data Mapper: A layer that translates between domain objects and database rows while keeping the two independent of each other.DEFINED IN Objects that do not know they are stored
Data mart: A table or set of tables shaped for one team's questions and encoding that team's specific definitions.DEFINED IN Refinement stages
Data mesh: An organisational approach, named by Zhamak Dehghani in 2019, built on domain ownership, data as a product, a self-serve platform, and federated computational governance.DEFINED IN Federated data ownership
Data minimisation: Collecting and retaining only what a purpose requires, which removes paths rather than defending them.DEFINED IN Data leakage paths
Data observability: Continuous monitoring of freshness, volume, schema, and distribution to detect pipeline failure.DEFINED IN Wrong with nothing missing
Data owner: The accountable party who decides permitted uses and access, and bears the consequences of those decisions.DEFINED IN Three kinds of responsible person
Data ownership: The rule that exactly one system is authoritative for a given record at a time.DEFINED IN Replacing a system you cannot turn off
Data plane: The per-request path that forwards, serves, or processes traffic using configuration it already holds.DEFINED IN Control plane and data plane
Data plane / control plane: The proxies that carry traffic, versus the component that configures them and issues identities.DEFINED IN Moving failure handling out of the program
Data poisoning: Deliberately placing content into a training corpus so a model learns a chosen behaviour from it.DEFINED IN Poisoning the well
Data product: A dataset published deliberately for others, with documentation, a schema, quality guarantees and a named owner.DEFINED IN Federated data ownership
Data profiling: Inspecting actual values to infer a column's type, range, cardinality, and relationships.DEFINED IN Six names for one field
Data race: Two unordered accesses to the same location where at least one is a write; undefined behaviour in most memory models.DEFINED IN Immutability
Data skipping: Excluding files or row groups using recorded min-max statistics rather than partition structure.DEFINED IN Partition pruning
Data steward: The curator of a dataset's meaning: definitions, business rules, quality, and edge cases.DEFINED IN Three kinds of responsible person
DataLoader: The batching-and-caching pattern that collects field requests within a tick and issues a single combined fetch.DEFINED IN Letting callers ask for exactly what they want
Days of supply: Stock divided by an assumed daily consumption rate; meaningless without naming the rate.DEFINED IN Munitions stockpiles
De facto standard: One established by widespread adoption of a particular implementation, with no prior agreement.DEFINED IN Technical standards
De jure standard: One set out in a published document by a standards body or regulator, existing independently of any product.DEFINED IN Technical standards
De novo review: Review from scratch, owing the court below nothing, applied to questions of law.DEFINED IN Appellate deference
Deaccession: A library's removal of an item from its permanent collection, typically driven by borrowing statistics.DEFINED IN Canon formation
Dead band: The deliberate gap between switch-on and switch-off temperatures that stops a relay chattering.DEFINED IN Thermostat overshoot
Dead ground: Ground an attacker can occupy that no defender is able to fire into.DEFINED IN Obsolete fortifications
Dead time: An interval during which a change produces no response at all, after which the full response begins.DEFINED IN Measurement dead time
Dead-hand problem: The objection that the entrenched choices of past generations bind people who never consented to them.DEFINED IN Constitutional entrenchment
Dead-letter queue: A separate destination where a broker places a message after too many failed delivery attempts.DEFINED IN Poison messages · When responsibility transfers
Death effect: The measured change in an artist's auction prices around and after their death.DEFINED IN Death and art prices
Deborah number: The relaxation time divided by the observation time; large means the material reads as solid, small as liquid.DEFINED IN Viscoelastic putty
Debye relaxation: The broad frequency response of dipoles too sluggish to follow a fast field; the correct model here, not resonance.DEFINED IN Selective heating
Decapitation strike: An attack aimed at the leadership and command network rather than at the weapons themselves.DEFINED IN Delegated launch authority
Decay constant (λ): The probability per unit time that a nucleus decays; the single physical input to the law.DEFINED IN Radioactive half-life
Deception: Deliberately presenting an opponent with observable evidence, most effective when it agrees with what he already believes.DEFINED IN Fog of war
Decibel: Ten times the base-ten logarithm of a power ratio; doubling power is 3.01 dB.DEFINED IN Massed string sound
Decision tree model: Representing an algorithm as a binary tree of queries, with outputs at the leaves, in order to reason about all algorithms of that kind.DEFINED IN The sorting floor
Declination: A documented decision not to pursue a case that could have been pursued.DEFINED IN Enforcement discretion
Decode: The serial loop producing one output token per step, each conditioned on the last.DEFINED IN Prefill and decode · Time to first token
Deconditioning: The coordinated loss of cardiovascular, muscular and bone capacity when habitual demand is withdrawn.DEFINED IN Bed rest harm
Decontamination: Removal of agent from people, equipment and terrain, which takes a unit out of action for its duration.DEFINED IN Chemical protective posture
Decorator: An object implementing the same interface as the one it holds, adding behaviour before or after delegating to it.DEFINED IN Wrapping without changing
Decoupling: The property a buffer provides: making two stages independent for a bounded interval.DEFINED IN Just-in-time fragility
Decoy effect (asymmetric dominance): Adding an option clearly worse than one existing option but not another, shifting choice toward the one that dominates it; a real finding whose replication in realistic settings is mixed.DEFINED IN The dish nobody orders
Dedifferentiation: A specialised cell reverting to a less committed, dividing state.DEFINED IN Limits of regeneration
Deep homology: Independently evolved structures built using the same ancient genetic toolkit.DEFINED IN Convergent evolution
Deep structure: The underlying principle or relational pattern a problem instantiates.DEFINED IN Transfer of learning
Default: The behaviour chosen when the user expresses no preference, and therefore the case governed entirely by prediction.DEFINED IN Least astonishment
Default option: The outcome that follows if the chooser does nothing, and the beneficiary of a shift away from effortful comparison.DEFINED IN Decision fatigue · Subscription inertia
Defeater: A specific reason to doubt a claim or its source, which cancels the default entitlement to believe it.DEFINED IN Knowledge from testimony
Defence in depth: Stacking safeguards so that no single failure reaches the consequence; only effective when the layers fail for different reasons.DEFINED IN Guardrails · Talked out of its own rules
Definitive host: The host in which the parasite reproduces sexually, here the grazing mammal.DEFINED IN Parasite host manipulation
DEFLATE: The widely used format combining a Lempel-Ziv pass with Huffman coding.DEFINED IN Lossless compression
Deflation: A fall in the price level, which rewards holding money rather than spending it.DEFINED IN What is inflation?
Degenerate pair: Two modes of identical frequency related by a symmetry, which split into two close frequencies when the symmetry is broken.DEFINED IN Cracked bell tone
Degenerate tree: A search tree that has collapsed into a chain, where lookups cost linear time.DEFINED IN A tree that rearranges itself
Degenerating research programme: Lakatos's term for a programme whose repairs only accommodate known results rather than predicting new ones.DEFINED IN Scientific testability
Degree Heating Weeks (DHW): Accumulated thermal stress: weeks of temperature above the local maximum monthly mean plus one degree.DEFINED IN Coral bleaching
Deidentification: Withdrawal from a domain a sibling has claimed, as active differentiation from them.DEFINED IN Sibling deidentification
Delay-retention effect: The finding that feedback given after a delay can produce better later retention than immediate feedback.DEFINED IN Feedback timing
Delayed neutrons: The fraction, about 0.65 per cent in uranium-235, emitted seconds after fission by decaying fragments.DEFINED IN Critical mass
Delegated authority: An arrangement where one identity acts on behalf of another, so the acting party and the answerable party differ.DEFINED IN The audit record as the product
Delegation: Forwarding work to a held object, the mechanism by which composition achieves reuse.DEFINED IN Composition over inheritance
Deliberate practice: Effortful practice at tasks just beyond current ability, with immediate informative feedback and repetition with correction.DEFINED IN Deliberate practice
Delimiter: A marker such as an XML-style tag or a fence that separates supplied content from surrounding instructions.DEFINED IN Delimiters as a boundary
Delocalised electron: An electron not confined to one bond, free to move through a region and carry current.DEFINED IN Carbon allotropes
Delta: The membrane-bound ligand that activates Notch on a touching cell, restricting the signal to direct contact.DEFINED IN Lateral inhibition in tissue
Delta notation (per mil): A sample's isotope ratio expressed as parts per thousand deviation from a standard.DEFINED IN Rainfall isotope distillation
Delta-v: The total change in velocity a stage requires or can deliver, the common currency of rocket design.DEFINED IN Rocket staging
Demand risk: The risk that committed capacity goes unsold; what the wholesale discount pays for.DEFINED IN Package tour pricing
Demand sharing: Transfer initiated by the receiver's request, where the sanctioned act is refusing rather than failing to offer.DEFINED IN Sharing under scarcity
Demand-pull inflation: Prices rising because spending outruns what the economy can produce.DEFINED IN What is inflation?
Demarcation: The boundary defining which trade may perform which work, often reinforced by certification and insurance rather than skill alone.DEFINED IN Trade demarcation
Demesne: The portion of an estate farmed for the lord's own account rather than let to tenants.DEFINED IN Second serfdom
Demonstrative reasoning: Inference whose denial is a contradiction, as in mathematics.DEFINED IN Problem of induction
Denaturation: The loss of a protein's folded three-dimensional shape under heat, acid or agitation.DEFINED IN Setting a stain
Denied boarding: Being refused a seat on an oversold flight; voluntary when compensation is accepted, involuntary when no volunteer is found.DEFINED IN Overbooking
Denormalization: Deliberately storing redundant or precomputed data to reduce read-time work.DEFINED IN Denormalization
Dense retrieval: Scoring by similarity between learned vector representations of query and document.DEFINED IN Hybrid search
Density: How many independent tenants one physical machine can hold at once.DEFINED IN Isolates, containers, and startup cost
Density coefficient: An assumed number of persons per unit of settled area or roofed floor, taken from comparative settlements rather than the site being estimated.DEFINED IN Ancient population estimates
Density test: Checking whether cases pile up on the favourable side of a threshold, which would indicate the running variable was manipulated.DEFINED IN Class-size cutoff rules
Denylist: A distributed record of revoked token identifiers consulted at verification time.DEFINED IN You cannot un-issue a signature
Dependency inversion: Arranging source-code dependencies to point from concrete, volatile modules toward abstractions owned by higher-level policy.DEFINED IN Dependency direction
Depletion (consumptive use): The volume that leaves the basin's usable stock, chiefly by transpiration and evaporation.DEFINED IN Irrigation efficiency paradox
Depletion zone: The shell of soil around an absorbing root from which a poorly mobile ion has been stripped faster than it is resupplied.DEFINED IN Mycorrhizal carbon trade
Deploy/release decoupling: Treating "code is on the servers" and "behaviour is visible to users" as two separately controlled events.DEFINED IN Feature flags
Deposition: The settling of transported particles when the flow carrying them slows below the speed needed to hold them.DEFINED IN Silted harbours
Depth hoar: Large, striated, cup-shaped crystals formed by strong vapour transport, weakly bonded to each other.DEFINED IN Depth hoar in snowpack
Derating: Reducing an allowed current because the installation removes heat less effectively than the reference case.DEFINED IN Coiled extension lead
Derby fishery: A fishery in which a shared limit compresses the season into a sprint.DEFINED IN Race to fish under quota
Derived store: A copy of data created for a secondary function, such as an index, cache or warehouse, with its own access model.DEFINED IN Data leakage paths
Derived value: A stored value computable from other stored data, such as an order total.DEFINED IN Denormalization
Dermatome: The strip of skin whose sensation is carried by a single spinal nerve root.DEFINED IN Referred pain
Descriptive norm: Perception of what people actually do, as distinct from an injunctive norm about what they ought to do.DEFINED IN Everyday legal compliance
Design by contract: Meyer's method of specifying components as mutual obligations, implemented natively in Eiffel and as aspects in Ada 2012.DEFINED IN Design by contract
Design effect: The ratio by which clustering, stratification, and weighting inflate or deflate variance relative to simple random sampling.DEFINED IN Sample size versus population
Design pressure: The tendency of a difficult-to-write test to reveal unwanted coupling in the code being tested.DEFINED IN Writing the test first
Designated carer: The family member who ends up performing most caregiving, typically without an explicit appointment.DEFINED IN Caregiving load
Desirable difficulty: A condition that slows practice performance while improving long-term retention and transfer.DEFINED IN Feedback timing · Fluency illusion · Interleaved practice · Retrieval practice · Spacing effect
Desire line: The route people actually take, revealed by their behaviour rather than by the plan.DEFINED IN The paved road · Unplanned settlement form
Detection versus warning: Detection confirms an agent is present; warning is prior information that one may arrive, and only warning can inform the decision in time.DEFINED IN Chemical protective posture
Determinism: The thesis that the state of the world plus the laws of nature fix every later state.DEFINED IN Free will · Replay determinism
Deterrence: The account of obedience as a weighing of gain against expected punishment, formalised for crime by Gary Becker.DEFINED IN Everyday legal compliance · Randomized screening
Detraining: The loss of trained adaptations when the stimulus is reduced or removed for too long.DEFINED IN Training taper
Detrending: Removing the growth trend a tree shows purely from ageing, to isolate climate signal.DEFINED IN Tree-ring evidence
Deuterium excess: Deuterium delta minus eight times oxygen-18 delta, a tracer of the kinetic conditions at the moisture source.DEFINED IN Rainfall isotope distillation
Diagnosticity: How much an event tells you about someone's stable disposition, which is often higher for unconstrained trivial acts than for dramatic ones.DEFINED IN The small last straw · Trust asymmetry
Diamond dependency: Two dependency paths from one program that converge on the same shared package at different versions.DEFINED IN Dependency conflicts
Diapason normal: The French standard of 1859 setting the orchestral A at 435 cycles per second.DEFINED IN Concert pitch standard
Dichotic listening: An experiment presenting different messages to each ear, with the listener shadowing one.DEFINED IN Cocktail party effect
Dielectric heating: Heating produced when an alternating field drives charge reorientation that lags the field and dissipates energy.DEFINED IN Selective heating
Difference-in-differences: Comparing the change over time in an affected group with the change in an unaffected one, stripping out shocks common to both.DEFINED IN New crops and population growth
Differential aeration cell: A corrosion cell driven by unequal oxygen access at two connected points on the same metal, with the starved region becoming the anode.DEFINED IN Crevice corrosion
Differential item functioning: An item behaving differently for two groups matched on ability; here, the signal that an anchor has stopped being stable.DEFINED IN Exam equating
Differential pressure: The difference between inside and outside pressure, and the load the fuselage must carry.DEFINED IN Airplane cabin pressure
Differential privacy: A guarantee bounding how much any single individual's data can influence a published result.DEFINED IN Re-identification of anonymized data
Differential rotation: The Sun's equator rotating faster than its poles, roughly 25 days against 34.DEFINED IN Solar cycle
Differential testing: Comparing two implementations on the same inputs, treating disagreement as the signal.DEFINED IN Running both and comparing
Differential undercount: Coverage error that varies systematically by group or place, rather than being spread evenly across the population.DEFINED IN Census undercount
Diffraction: The spreading of a wave into the geometric shadow of an obstacle, significant when the obstacle is comparable to the wavelength.DEFINED IN Radio diffraction
Diffuse field: The idealised condition of sound energy spread evenly through a room and travelling equally in all directions.DEFINED IN Concert hall reverberation
Diffusible hydrogen: Hydrogen dissolved in the lattice and free to move through it, as distinct from hydrogen trapped irreversibly at inclusions.DEFINED IN Delayed weld cracking
Diffusion: The spread of a story between cultures by contact, as opposed to independent invention.DEFINED IN Story shape
Diffusion flame: A flame in which fuel and oxidiser arrive from opposite directions and react where they meet, as opposed to a premixed flame.DEFINED IN Candle wick
Diffusion of responsibility: The felt obligation to act divided among all who could act, so each feels less of it.DEFINED IN Bystander effect
Diffusion sensing: The alternative reading in which the cell is measuring how well its surroundings retain secreted molecules, not how many neighbours it has.DEFINED IN Quorum sensing
Diffusion-limited oxidation: The confinement of oxidative damage to a surface layer, set by how fast oxygen enters relative to how fast it is consumed.DEFINED IN Plastic weathering
Digest: A cryptographic hash used as an artefact's address, so the reference cannot be true of different content.DEFINED IN Provenance of what you deploy · Tags versus digests
Digit test: An audit comparing observed leading-digit frequencies against the Benford distribution to flag data worth inspecting.DEFINED IN Benford's law
Dijkstra's algorithm: The nearest-first method itself, published in 1959; with a binary heap it runs in O((V + E) log V) time.DEFINED IN Nearest first
Dilatancy: The requirement that a densely packed granular bed expand in order to shear, first described by Reynolds in wet sand.DEFINED IN Shear-thickening food pastes
Dilation: The expansion a packed granular bed must undergo before any grain can move past another.DEFINED IN Brazil-nut effect
Dilution: The fall in the ratio of experienced to inexperienced personnel inside a unit when it expands faster than experience accumulates.DEFINED IN Training cadre bottleneck
Dilution of precision: The factor by which satellite geometry magnifies a ranging error into aDEFINED IN How does GPS find your location?
Dimension table: A table describing an entity, such as a customer, that fact rows refer to.DEFINED IN Surrogate keys
Dimictic: Of a lake that fully mixes twice a year, in spring and autumn.DEFINED IN Lake turnover
Diminishing marginal utility: The principle that each additional unit of wealth adds less usefulness than the one before it.DEFINED IN Insurance
Diminishing returns: The pattern where each doubling of a resource yields a smaller gain than the one before.DEFINED IN Thinking budget
Dipole: A molecule with separated positive and negative charge centres, on which an electric field exerts a torque.DEFINED IN Selective heating
Dipole radiation: The field emitted by an oscillating charge, maximal perpendicular to its motion and zero along it.DEFINED IN Brewster angle glare
Direct addressing: Using the key itself as an array index; possible only when the universe of keys is small enough to allocate a slot for each.DEFINED IN Finding without searching
Direct displacement: A household forced out by eviction, demolition or a rent rise it cannot meet.DEFINED IN Gentrification
Direct network effect: Value to a user rises with the number of users of the same kind, as with a telephone network.DEFINED IN Network effects
Direct replication: A repeat of a study's original procedure, intended to test whether its result recurs.DEFINED IN Note-taking by hand
Direct store delivery: Shipping from supplier straight to the retail outlet, bypassing the depot entirely.DEFINED IN Cross-docking
Direct-acting antiviral: A drug binding a virus-encoded protein directly, rather than modulating the host response.DEFINED IN Antiviral difficulty
Directed acyclic graph: A directed graph containing no cycle; exactly the condition under which a valid order exists.DEFINED IN Order from pairwise rules
Directed deterrence: A defence that repels the consumers that destroy seeds while leaving the ones that disperse them unaffected, as capsaicin does with rodents and birds.DEFINED IN Sweet fruit, guarded seed
Directional constancy: The ratio of the vector-mean wind to the mean wind speed; near one where a terrain-locked flow dominates.DEFINED IN Katabatic winds
Directional freezing: Insulating all faces but one so the ice front advances one way, with liquid open ahead of it throughout.DEFINED IN Cloudy ice cubes
Directive: An order that assigns an objective and constraints rather than prescribing the actions to reach it.DEFINED IN Mission command
Director: The local average direction of the molecular long axes; the field a display actually controls.DEFINED IN Liquid crystals
Dirty read: Reading data written by a transaction that has not committed and may still roll back.DEFINED IN Database transactions
Disamenity: A local characteristic people will pay to avoid, such as smoke, noise or smell, which shows up in lower land values.DEFINED IN Windward wealth divide
Discard command: How a filesystem tells a drive that certain addresses no longer hold wanted data.DEFINED IN Write amplification
Discontinuous shear thickening: An abrupt rise in viscosity, often by orders of magnitude, above a critical applied stress.DEFINED IN Shear-thickening food pastes
Discounting: The reduction in a reward's present felt value as its delay increases.DEFINED IN Weakness of will
Discovery rule: A provision starting the clock when the claimant knew or ought to have known of the claim, rather than when the act occurred.DEFINED IN Statutes of limitation
Discretionary effort: The contribution a worker chooses to make beyond what is formally required, and can therefore withdraw without breaching anything.DEFINED IN Working to rule
Discriminative contrast: The account in which juxtaposing unlike items makes their differences perceptible, training the selection step.DEFINED IN Interleaved practice
Discursive dilemma: The result that majority voting on premises and on the conclusion they entail can commit a group to opposite verdicts, so group attitudes are not a simple function of members' attitudes.DEFINED IN Collective responsibility
Disfluency: Any interruption to the flow of speech: filled pause, repetition, false start or self-repair.DEFINED IN Filler words · Transcribed speech
Dishabituation: The immediate restoration of a habituated response by a novel strong stimulus, the standard evidence that habituation is not fatigue.DEFINED IN Habituation versus sensitization
Disinflation: A slowing of the inflation rate; prices still rise, only more gently.DEFINED IN What is inflation?
Dislocation: A line defect in a crystal along which slip can propagate one atomic row at a time.DEFINED IN Alloy strength · Work hardening
Dislocation density: Line length per unit volume; its square root sets the added strength.DEFINED IN Work hardening
Dispersal: Abandoning concentration so as to present no target, which removes the value of an opponent's firepower.DEFINED IN Holding conquered ground
Dispersion forces: Weak attractions arising from fluctuating charge distributions, responsible for holding graphite's sheets together.DEFINED IN Carbon allotropes
Displacement: The volume of water a floating hull pushes aside, equal in weight to everything aboard.DEFINED IN Rowing crew scale · Shoot-and-scoot artillery
Displacement cost: The value of the future booking that accepting this one would rule out.DEFINED IN Different prices, same room
Displacement cost (bid price): The revenue a hotel expects to forgo later by selling a room tonight; computed per night, and the number every acceptance decision is measured against.DEFINED IN Length-of-stay controls · Shoulder-season price cliff
Displacement effect: A benefit to participants that comes partly at the expense of non-participants competing for the same fixed resource.DEFINED IN Pilot-to-scale failure
Displacive transformation: A change of phase in which atoms move less than one bond length and keep their neighbours.DEFINED IN Shape-memory alloys
Disposable soma: Kirkwood's account: repair competes with reproduction for resources, so optimal body maintenance is finite.DEFINED IN Senescence
Disposition: What happens at the end of retention: destruction, anonymisation, or transfer to archive.DEFINED IN Data you keep is data you can lose · Labelling before deciding
Dispositional attribution: Explaining behaviour by a person's stable traits, intentions, or abilities.DEFINED IN Attribution asymmetry
Disruptive innovation: An offering that starts cheaper and worse on the mainstream dimensions, then improves until it is good enough.DEFINED IN Incumbent disruption
Disseminated intravascular coagulation: Widespread small-vessel clotting that consumes clotting factors and platelets, causing thrombosis and bleeding at once.DEFINED IN Sepsis
Dissimilar redundancy: Deliberately different designs, suppliers, or locations for redundant channels, so that fewer causes are shared.DEFINED IN Engineered redundancy
Distant blockade: Watching the exits from the open sea rather than lying off the enemy's port, adopted as close watch became too dangerous.DEFINED IN Fleet in being
Distinguishability: The degree to which a state's defensive preparations can be told apart from preparations for attack.DEFINED IN Security dilemma
Distinguishing: Holding an earlier rule inapplicable because the material facts differ.DEFINED IN Legal precedent
Distraction theory: The account that pressure occupies working memory, harming tasks that depend on it.DEFINED IN Choking under attention
Distractor: An incorrect option on a multiple-choice item; well built, it is the answer one specific wrong procedure produces.DEFINED IN Diagnostic distractors
Distributed monolith: Services that must be released together, incurring every distributed cost while keeping the coordination they were meant to remove.DEFINED IN Splitting a system into services · The distributed monolith
Distributed practice: Study spread across separated sessions, as opposed to massed practice concentrated in one.DEFINED IN Spacing effect
Distributed representation: Information held across many parameters at once, none of which holds it alone.DEFINED IN Where a fact lives in a model
Distributional hypothesis: The observation that words appearing in similar contexts tend to have similar meanings.DEFINED IN Embedding space
Distroless: A minimal base image containing a language runtime and certificates but no shell or package manager.DEFINED IN Building somewhere you do not ship from
Diurnal Yarkovsky effect: The rotation-driven variant described here, expanding prograde rotators' orbits and shrinking retrograde ones.DEFINED IN Yarkovsky effect
Divergence (of a series): The property of a sum growing without bound as more terms are added.DEFINED IN Infinitude of primes
Diversification: Playing several sports during childhood before narrowing, as distinct from specializing early.DEFINED IN Early sport specialization
Divide and conquer: Subsidising one side to attract it, then recovering the cost from the side that wants it.DEFINED IN Two-sided market launch
Doctrine: An army's codified expectation of how it will fight, taught in its schools and embedded in its structure and equipment.DEFINED IN Doctrine lag
Doctrine of double effect: The principle that harm intended as a means or end is harder to justify than equal harm merely foreseen as a side effect.DEFINED IN Doing versus allowing
Doherty threshold: The observation from IBM's 1982 work that response times under roughly 400 milliseconds keep a user engaged rather than merely tolerant.DEFINED IN Time to first token
Domain: A bounded sphere of life with its own participants and setting, within which a particular language is normally used.DEFINED IN Heritage language loss
Domain of validity: The range of conditions a fitted rule was tuned on, outside which it gives no warning it has stopped applying.DEFINED IN Rules of thumb on site
Domain team: The team that operates a business capability and therefore holds the knowledge of what its data means.DEFINED IN Federated data ownership
Domain-language recovery: Restoring the business vocabulary that a system's identifiers obscure.DEFINED IN Recovering what the business meant
Domar's hypothesis: Evsey Domar's argument that free land, free peasants, and a non-working landowning class cannot all exist at once.DEFINED IN Post-plague wages · Second serfdom
Domestication syndrome: The cluster of body, behaviour and breeding traits that recurs across domesticated lineages.DEFINED IN Domestication
Domestique: A rider whose result is defined by a team leader's finish rather than his own.DEFINED IN Drafting in the peloton
Dominance duration: The length of one uninterrupted spell of seeing one image; measured distributions are right-skewed and nearly uncorrelated from spell to spell.DEFINED IN Binocular rivalry
Dominant strategy: A choice at least as good as any alternative no matter what others do.DEFINED IN Auction prices
Doppler limit: The temperature ħΓ/2*k*B at which cooling balances recoil heating, beaten in practice by sub-Doppler cooling.DEFINED IN Laser cooling
DORA: The DevOps Research and Assessment programme, whose surveys established the four delivery measures cited here.DEFINED IN Deploying more to break less
Dormancy: The persistence of disseminated tumour cells without growth, sometimes for many years.DEFINED IN Metastasis
Dormant code: Code that is reachable and correct but whose triggering condition occurs rarely, such as annually.DEFINED IN Code that never runs, and code that runs once a year
Dorsal horn: The sensory region of the spinal cord grey matter where incoming afferents first synapse.DEFINED IN Referred pain
Dose-response: The requirement that a proposed cause produce more of its effect when more of it is present.DEFINED IN Twin language delay
Double coincidence of wants: The requirement, under barter, that each party wants what the other offers.DEFINED IN Origin of money
Double-checked locking: A lazy-initialisation idiom that was unsafe in Java before the JSR-133 memory model revision in Java 5.DEFINED IN The singleton regret
Doublet: Two words in one language descended from the same ancestor by different routes, such as cattle and capital.DEFINED IN Loanword doublets
Downward nominal wage rigidity: The observed reluctance of the money figure on a payslip to fall, even when real wages could adjust.DEFINED IN Wage stickiness
Dowry: Property transferred with the bride, usually from her natal family, forming the new household's fund.DEFINED IN Bridewealth and dowry
Doxastic voluntarism: The view that beliefs can be formed by an act of will; direct versions are widely rejected, indirect versions widely accepted.DEFINED IN Believing at will
DPoP (RFC 9449): Demonstrating Proof of Possession, an application-layer scheme binding a token to a key the client must prove it holds.DEFINED IN Detecting a theft you cannot see
Drafting: Riding in the disturbed air behind another rider, sharply reducing the power needed to hold a given speed.DEFINED IN Drafting in the peloton
Drag area: The product of drag coefficient and frontal area, the shape-dependent term that setsDEFINED IN Climbing versus descending weight
Drag coefficient: A dimensionless number capturing how much resistance a shape produces for its frontal area; near 0.5 for a sphere in this regime.DEFINED IN Terminal velocity of raindrops
Drag crisis: The abrupt fall in drag coefficient when a sphere's boundary layer becomes turbulent and the wake narrows.DEFINED IN Golf ball dimples · Magnus effect
Drainage divide: The line separating two catchments, located wherever their opposing erosion fronts currently meet.DEFINED IN River capture
Drift: The accumulated difference between a system's actual state and the state its configuration describes.DEFINED IN Configuration drift
Driver: The power supply inside an LED lamp that converts mains into a regulated current for the diodes.DEFINED IN Ghost glow in LED bulbs
Droop control: A governor setting that makes a generator's output rise in proportion to a fall in frequency, sharing response automatically.DEFINED IN Grid balancing
DRY: The principle that every piece of knowledge should have one authoritative representation in a system; often misquoted as a ban on repeated text.DEFINED IN When removing duplication hurts
Dry adiabatic lapse rate: The cooling of an unsaturated rising parcel, about 9.8 degrees Celsius per kilometre.DEFINED IN Cooling with altitude · Rain shadow
Dry mass: Everything that is not propellant: tanks, engines, structure, avionics, payload.DEFINED IN Rocket staging
Dry valley: A surface channel abandoned when its stream was captured underground.DEFINED IN Sinking streams in karst
Drying oil: An oil unsaturated enough to harden into a solid film in air, the class that includes linseed oil.DEFINED IN Cast-iron seasoning
Dual career ladder: A structure offering advancement in pay and rank along a specialist track, without requiring a move into management.DEFINED IN Promotion mismatch
Dual systems model: The account in which reward sensitivity and cognitive control mature on different timetables, leaving a window where one outpaces the other.DEFINED IN Adolescent risk
Dual write: Two systems independently writing the same truth; a common source of silent divergence.DEFINED IN Replacing a system you cannot turn off
Dual-system estimation: The capture-recapture method that infers those missed by both the census and the survey from the overlap between them.DEFINED IN Census undercount
Dual-write problem: The impossibility of atomically updating two independent systems without a coordinating protocol.DEFINED IN The outbox
Ductile: Able to deform permanently before fracturing, which both warns of overload and sheds it.DEFINED IN Marble supports
Ductile-to-brittle transition: The temperature range over which a steel's toughness falls sharply, voiding a case made warm.DEFINED IN Leak-before-break
Duhem-Quine thesis: The argument that hypotheses face the evidence only in bundles, so a failed test cannot single out the guilty member.DEFINED IN Scientific testability
Durable execution: An execution model in which a program's progress is persisted as a record of results, so the program can be resumed on any machine after a failure.DEFINED IN Durable execution
Durable memory: Facts promoted out of a conversation to persist between sessions, as distinct from the context window.DEFINED IN What an assistant should forget
Duration neglect: The weak influence of how long an experience lasted on how it is remembered.DEFINED IN Remembered holidays
Duty to protect: The obligation on a therapist, from the Tarasoff cases, to act when a patient presents a serious danger to an identifiable person.DEFINED IN Guaranteed secrecy
Dwell time: The interval a passenger spends airside between clearing screening and boarding.DEFINED IN Airport layout
Dyadic time: One-to-one interaction between a caregiver and a single child, in which speech can be tuned to that child's attention.DEFINED IN Twin language delay
Dynamic control flow: The pattern where what runs next is decided at run time by generated output rather than by fixed code.DEFINED IN The agent loop
Dynamic dispatch: Resolving the target of a call at run time, which hides the edge from static analysis.DEFINED IN Code that never runs, and code that runs once a year
Dynamic equilibrium: A state in which two opposing processes continue at equal rates, so nothing changes overall despite constant activity.DEFINED IN Freezing-point depression
Dynamic equivalence: A translation aimed instead at producing on its reader an effect comparable to the original's.DEFINED IN Translation equivalence
Dynamic packaging: Assembling a holiday from live inventory at the moment of sale, without committing to capacity in advance.DEFINED IN Package tour pricing
Dynamic power: The power a circuit dissipates while switching, rising with the square of supply voltage and with clock frequency.DEFINED IN Thermal throttling
Dynamic range compression: Automatic gain reduction of louder passages, allowing the whole signal to be raised afterwards.DEFINED IN Broadcast loudness
Dynamic recovery: Annihilation of opposite-signed dislocations, capping how far a metal hardens.DEFINED IN Work hardening
Dynamic voltage and frequency scaling: Adjusting clock and supply voltage together at runtime, the lever a throttling controller actually pulls.DEFINED IN Thermal throttling
Dysphemism: A deliberately harsh term chosen in place of a neutral one, the treadmill's mirror image.DEFINED IN Euphemism
Dzhanibekov effect: The name often given to the same flip when it is observed in weightlessness.DEFINED IN Intermediate axis instability

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Eager rebalancing: The protocol in which every member revokes every partition before a new assignment is computed.DEFINED IN Why adding a worker stops the others
Ear-voice span (décalage): The lag between hearing a stretch of source speech and producing its rendering; the field's main measurable for this trade-off.DEFINED IN Simultaneous interpreting
Early filter: The proposal that unattended channels are rejected before meaning is extracted.DEFINED IN Cocktail party effect
Early mobilisation: The deliberate practice of getting patients upright and walking soon after surgery or acute illness.DEFINED IN Bed rest harm
Early reflections: The first returns from nearby surfaces, arriving soon enough to fuse with the direct sound and shape clarity and spaciousness.DEFINED IN Concert hall reverberation
Early stopping: Ending training at the point where held-out error stops improving.DEFINED IN Overfitting
Earmarking: Labelling a sum for a purpose, making it harder to spend on anything else.DEFINED IN Household money pots
Earnshaw's theorem: No static arrangement of fixed charges or dipoles gives stable equilibrium, because the energy is harmonic and harmonic functions have no interior minima.DEFINED IN Superconducting levitation
Eccentric contraction: A muscle producing force while being lengthened, as in lowering a weight or walking downhill.DEFINED IN Delayed muscle soreness
Eccentric loading: Muscle generating force while lengthening, the mechanism by which a body isDEFINED IN Climbing versus descending weight
Eccentricity: How stretched an orbit is, from zero for a circle toward one for a near-parabola.DEFINED IN Kirkwood gaps
Eccentricity, obliquity, precession: The three orbital parameters that vary on roughly 100,000, 41,000 and 23,000-year cycles.DEFINED IN Ice age triggers
Echelon: A level of command; each holds its own reserve, sized and timed to the surprises that level must answer.DEFINED IN Holding a reserve
Eclipse season: The roughly 33-day stretch during which the Sun lies close enough to a node for an eclipse to be possible.DEFINED IN Eclipse seasons
Eclipse year: About 347 days, the interval between successive passages of the Sun through the same node, shortened from the calendar year by the backwards drift of the nodes.DEFINED IN Eclipse seasons
Ecological risk hypothesis: The argument that language-group size is set by how far people must reach for insurance against bad years.DEFINED IN Mountain language diversity
Economic incidence: The party whose real income falls as a result of the tax.DEFINED IN Tax incidence
Economic rent: The payment a scarce asset commands purely for being what it is, here a position near the monument.DEFINED IN Landmark restaurants · Resource revenue and accountability
Economies of scale: Falling unit cost as output rises; a supply-side advantage frequently mislabelled as a network effect.DEFINED IN Network effects
Ecosystem engineer: A species that alters the physical habitat itself, such as a beaver damming a stream.DEFINED IN Keystone species
Ectopic discharge: Impulses generated somewhere along an axon rather than at its sensory ending.DEFINED IN Pins and needles
ED50 / LD50: The dose producing the desired effect, or death, in half of a tested population.DEFINED IN Dose-response
Edge angle: The tilt of the ski's base away from the snow surface.DEFINED IN Carving ski sidecut
Edge apex radius: The width of the rounded tip of an edge, the practical measure of how sharp it is.DEFINED IN Sharpness
Edge flaw: A microscopic chip left by cutting, from which a brittle fracture starts under tension.DEFINED IN Setting blocks
Editing signal: The audible break or word marking that what preceded it is to be discarded and a correction follows.DEFINED IN Filler words
Educational triage: Concentrating effort on pupils near a reporting threshold, where it moves the published figure most.DEFINED IN Teaching to the test
Effect size (standard deviation): A measure of an intervention's impact expressed in units of the spread of student outcomes, allowing comparison across different tests.DEFINED IN Tutoring versus class size
Effective exhaust velocity: How fast a rocket throws its propellant; the sole measure of engine efficiency in the equation.DEFINED IN Rocket staging
Effective population size (of learners): The number of practitioners a learner can actually sample from, which is what governs transmission fidelity, rather than the raw population.DEFINED IN Technology loss
Effective reproduction number: The same quantity in the real population, reduced by existing immunity and by behaviour.DEFINED IN Herd immunity
Effectively axiomatised: Having an axiom set a machine can recognise, so proofs are mechanically checkable.DEFINED IN Incompleteness
Effectively-once: The accurate name for the guarantee usually sold as exactly-once: delivery repeats, but the effect happens once.DEFINED IN Idempotent operations
Efference copy: An internal duplicate of a motor command, used to predict the sensory consequences of one's own movement.DEFINED IN Motion sickness · Self-tickling
Efficiency: Useful work out divided by work in; always below one, the shortfall leaving as heat.DEFINED IN Mechanical advantage
Efficiency gap: The difference between the parties' wasted votes as a share of all votes cast, proposed as a measure of partisan bias.DEFINED IN District boundaries
Efficiency wage: A wage set above the market-clearing level because doing so raises productivity enough to lower the cost of a given amount of work.DEFINED IN Paying above the market
Effort heuristic: The habit of inferring value from apparent effort expended, used when quality itself cannot be observed.DEFINED IN Paying for the five-minute fix
Ego depletion: The model of self-control as a consumable resource drained by any act of control; its central findings failed large pre-registered replication.DEFINED IN Decision fatigue · Worst behaviour at home
Egocentric bias in communication: A sender's tendency to judge their own message by the meaning they already hold in mind.DEFINED IN Text message tone
Egress charge: A per-gigabyte price on data leaving a provider's network, usually with inbound data free.DEFINED IN Metered cost
Egress path: Any route by which data can reach a reader outside the system that owns it, whether or not that route was designed as an interface.DEFINED IN Data leakage paths
Ejusdem generis: The canon that a general term following a list of specifics is read as limited to things of the same kind.DEFINED IN Statutory interpretation canons
Elastic rebound: The theory that rock bent by continued plate motion springs back when a locked fault finally slips, releasing the stored strain.DEFINED IN Why do earthquakes happen?
Elasticity: How much the quantity bought or sold changes in response to a price change.DEFINED IN Tax incidence
Elasticity of demand: How strongly a buyer's purchasing responds to price; the elastic buyer is the one who walks away, and the one who gets the discount.DEFINED IN Different prices, same room
Electrical double layer: The charged surface together with the diffuse cloud of counter-ions that screens it.DEFINED IN Colloid flocculation
Electrolyte: The conducting liquid film that lets ions complete the circuit, which salt makes far more effective.DEFINED IN Corrosion
Electron acceptor: The substance an organism dumps electrons onto to complete respiration; oxygen is only the most profitable of several.DEFINED IN Redox banding in sediment
Electron degeneracy pressure: Pressure arising from the exclusion principle rather than from heat, and therefore nearly independent of temperature.DEFINED IN Stellar hydrostatic balance
Electronic support: The passive interception and classification of an opponent's emissions.DEFINED IN Emissions control
Electronvolt: The energy unit convenient for atomic transitions, equal to the energy an electron gains crossing a one-volt difference.DEFINED IN Flame emission colours
Elite overproduction: A proposed mechanism in which too many contenders for too few elite positions drives internal conflict.DEFINED IN Societal collapse
ELT: Extract, load, transform: landing raw data in the warehouse and modelling it there with the warehouse's own engine.DEFINED IN Where the transform sits
Embedding: A vector representation of text produced so that texts with similar meaning land near each other.DEFINED IN Caching an answer nobody asked for exactly · Embedding space · Multimodal fusion · Tokenization · What a list of numbers remembers
Embedding inversion: Recovering the original text, exactly or approximately, from its embedding vector.DEFINED IN What a list of numbers remembers
Embedding similarity: The geometric closeness of two texts' vectors, used as the proxy for relevance.DEFINED IN Planting the source it will cite
Embodiment: The stronger claim that such mappings are grounded in bodily and sensorimotor experience and remain active during comprehension.DEFINED IN Metaphor
Embolism: A conduit rendered non-conducting by a gas bubble.DEFINED IN Cohesion-tension sap ascent · Midday stomatal closure
Emergence: A colony-level capability no individual possesses or represents.DEFINED IN Collective ant behavior
Emission spectrum: The set of discrete wavelengths an excited atom or molecule emits, fixed by the gaps between its energy levels.DEFINED IN Flame emission colours
Emissions control (EMCON): A deliberate, graded restriction on what a unit is permitted to transmit, set against a particular threat.DEFINED IN Emissions control
Emissivity: How well a surface radiates compared with a perfect emitter, between zero and one.DEFINED IN Spacecraft cooling
Emlen funnel: A funnel-shaped cage with a marking surface, in which a caged migrant's restless hops record the direction it is trying to go.DEFINED IN How do birds know where to migrate?
Emotion regulation: The capacity to modulate the intensity and duration of an emotional response rather than acting it out whole.DEFINED IN Toddler tantrums
Emphasis framing: Accounts that select and foreground different true aspects of the same event, common in news coverage.DEFINED IN Framing
Empirical equivalence: The relation between theories with the same observational consequences.DEFINED IN Underdetermination of theory
Empty name: A name with no bearer, such as "Holmes" or "Vulcan".DEFINED IN Talking about what does not exist
Emulation: Reproducing the original hardware or software environment so unchanged bits remain usable.DEFINED IN Digital preservation churn
Emulsion: Droplets of one liquid dispersed through another they do not mix with, kept apart by something at the interface.DEFINED IN Butter from cream · Soap cleaning
Enantiomer: One of two mirror-image forms of a molecule; carvone's two forms smell of spearmint and caraway.DEFINED IN Smell coding
Enantiomers: The two mirror-image forms of a chiral molecule, identical in every property that has no handedness of its own.DEFINED IN Molecular handedness
Enclave: Territory of one state lying wholly within another; the same parcel is an exclave when described from its own state's point of view.DEFINED IN Enclaves
Enclosure ratio: The relation of a space's height to its width, used to describe how contained or exposed it reads.DEFINED IN Architectural atmosphere
Encoder access: The ability to embed arbitrary text with the same model, which turns guessing into a scored search.DEFINED IN What a list of numbers remembers
Encoding specificity: The principle that retrieval succeeds when the cues present match those present when the memory was formed.DEFINED IN Shared memory in couples
End grain: The cut surface exposing the ends of the wood fibres, as at a sawn board end.DEFINED IN Screws in end grain
End-of-life signal: A distinct chirp emitted by an alarm that has passed its service date,DEFINED IN Night-time alarm chirp
End-to-end argument: The principle that a guarantee requiring endpoint knowledge cannot be fully provided by the layers beneath.DEFINED IN Exactly once is a property of the pipeline · Silent data corruption
Endemic disease: An infection that circulates continuously in a population rather than in waves.DEFINED IN Urban mortality
Endogenous sunk cost: A sunk outlay whose size the firm chooses, such as advertising or research, and which raises what buyers will pay.DEFINED IN Industry concentration
Endonym: The name a place or people uses of itself, in its own language.DEFINED IN Exonyms
Endorheic: Of a drainage basin having no outflow to the ocean, its water leaving only by evaporation and seepage.DEFINED IN Endorheic basins
Endospore: A dehydrated, multi-layered dormant structure built inside a mother cell that then lyses to release it.DEFINED IN Bacterial dormancy · Buffet holding time · Leftover spoilage
Endowment: Everything a person actually owns and controls, including their own labour power.DEFINED IN Famine amid plenty
Endowment effect: The tendency to value an object more highly once you own it than you would have paid to obtain it.DEFINED IN Clutter
Energetics: The propellants and explosive fills whose chemical plant is usually the deepest bottleneck in the chain.DEFINED IN Munitions stockpiles
Energy flux: The rate at which wave energy crosses a line, equal to energy density times propagation speed.DEFINED IN Tsunami shoaling
Enrolment versus attainment: Being registered at a school, as distinct from what is learned there; the two can move in opposite directions.DEFINED IN Remittances and the children left behind
Ensemble average: The mean over many parallel instances at a fixed time; time average — the long-run average along one trajectory.DEFINED IN Time average versus ensemble average
Ensemble forecast: Many model runs from perturbed initial states, whose spread estimates the day's available predictability.DEFINED IN Forecast horizon
Enthymeme: An argument with a premise left unstated, which is what nearly every real argument is.DEFINED IN What makes an argument logically valid?
Entitlement creep: The accumulation of permissions by an individual as they move between jobs without losing former access.DEFINED IN Roles as compression
Entity group: A set of related rows deliberately co-located on one shard so transactions over them stay local.DEFINED IN Sharding
Entrainment: Synchronization of attention or movement with a rhythm.DEFINED IN How can music create emotion? · Jet lag · Shift work · Shower curtain drift
Entrenchment: Deliberately raising the procedural cost of changing a rule above that of ordinary legislation.DEFINED IN Constitutional entrenchment
Entropic elasticity: A restoring force arising from the loss of accessible configurations rather than from stored bond energy.DEFINED IN Rubber elasticity
Entropy: A measure of how many microstates are consistent with a given macrostate.DEFINED IN Irreversibility
Entropy (Shannon): The average information per symbol of a source, and the lower bound on average code length.DEFINED IN Lossless compression
Entropy source: A physical process, such as thermal noise or oscillator jitter, supplying unpredictability that an algorithm cannot manufacture.DEFINED IN Pseudorandomness
Environmental determinism: The position that geography and climate largely determine the course of human societies, and the main charge levelled at this thesis.DEFINED IN East-west diffusion
Environmental lapse rate: The measured decrease with height in still air, averaging about 6.5 degrees per kilometre.DEFINED IN Cooling with altitude · Mass elevation effect
Ephemeris: The precise orbital description each satellite broadcasts about itself.DEFINED IN How does GPS find your location?
Epistemic modality: Grammatical or lexical marking of certainty, distinct from source.DEFINED IN Grammatical evidentiality
Epistemic uncertainty: The model's own ignorance about parameters or unfamiliar inputs, which more data can in principle reduce.DEFINED IN Confident model errors
Epistemic vigilance: The low-cost filtering people apply to what they are told, short of independent verification.DEFINED IN Knowledge from testimony
Epitope masking: The proposed mechanism whereby antibody bound to shared sites hides the antigen from B cells specific for the new sites.DEFINED IN Original antigenic sin
Equal-area: A projection preserving relative areas, at the cost of shape.DEFINED IN Map projection distortion
Equating: Placing scores from different forms of a test onto a common scale, so a given score means the same thing.DEFINED IN Exam equating
Equation of time: The yearly variation, up to about a quarter of an hour, between true and mean solar time.DEFINED IN Time zones
Equilibrium: The composition at which forward and reverse rates match, fixed by the free-energy difference between reactants and products alone.DEFINED IN Catalysis
Equilibrium constant: The fixed ratio of product to reactant activities a reaction settles at for a given temperature.DEFINED IN Ammonia synthesis
Equilibrium metamorphism: Curvature-driven rounding and bond thickening, which strengthens a layer.DEFINED IN Depth hoar in snowpack
Equilibrium relative humidity: The humidity of the air between kernels once balanced with the grain; the variable governing mould growth.DEFINED IN Grain bin hot spots
Equilibrium tide: The idealised static two-bulge shape the ocean would take if it could respond instantly, useful for the pattern but not the size.DEFINED IN Twice-daily tides
Equivalence framing: Two logically identical descriptions of the same outcomes, differing only in wording.DEFINED IN Framing
Equivalent single axle load (ESAL): Traffic expressed as a number of standard reference axles, converted using the fourth-power rule.DEFINED IN Road cracking
Erasure: A fault in which a piece is known to be missing, as distinct from corruption, where it is present but wrong.DEFINED IN Silent data corruption
Erbium-doped fibre amplifier: A pumped length of doped fibre that amplifies an optical signal directly, without converting it to electricity.DEFINED IN Guided light in fibre
Ergodic: The property that these two coincide; multiplicative wealth dynamics are not ergodic.DEFINED IN Time average versus ensemble average
Erlang C: The formula giving the probability that an arriving customer in such a system has to wait at all.DEFINED IN Single-queue service
Error: Setpoint minus measurement; the single quantity a feedback controller acts on.DEFINED IN Feedback control
Error budget: The amount of failure permitted by a reliability objective over a period, treated as a spendable allowance.DEFINED IN Error budgets
Error costs: The relative harm of the two directions of mistake, the input that sets any threshold.DEFINED IN Standards of proof
Error propagation: The way a mistake made early in a chain is treated as established fact by every later step.DEFINED IN Prompt chaining
Error propagation distance: The gap in code and time between where a fault is introduced and where it becomes observable.DEFINED IN Failing fast
Error-detection capability: The learner's own ability to judge, from internal signals, how far an attempt missed.DEFINED IN Practice feedback
Eruv: A boundary enclosing an area so that it counts as a single domain, permitting carrying within it on the Sabbath.DEFINED IN Ritual legal fictions
Erythrophobia: Persistent fear of blushing, self-sustaining because the fear increases self-focus and so the blushing.DEFINED IN Blushing
Erythropoietin (EPO): A hormone released mainly by the kidney in response to low oxygen delivery, stimulating red cell production.DEFINED IN Altitude training
Escalation ladder: Herman Kahn's scheme of graduated rungs, useful mainly as a shared vocabulary for where a crisis stands.DEFINED IN Escalation
Escalation of commitment: The organisational pattern of increasing investment in a failing course of action, often by the person responsible for starting it.DEFINED IN Sunk cost
Escalation rate: The share of requests that reach the expensive tier after starting cheap; the number that says whether a cascade is paying.DEFINED IN Model routing
Escape velocity: The speed a particle must reach to leave a body's gravity: about 5 km/s for Mars, 10.4 for Venus, 11.2 for Earth.DEFINED IN Martian atmosphere loss · What is a black hole?
Estrangement: A deliberate and sustained withdrawal of contact between relatives, as distinct from drifting apart.DEFINED IN Family estrangement
Eternity clause: A provision declared unamendable, as in Article 79(3) of the German Basic Law.DEFINED IN Constitutional entrenchment
Ethylene: A simple gaseous plant hormone that coordinates ripening, and can travel between unconnected fruits.DEFINED IN Ripening by contagion
ETL: Extract, transform, load: reshaping data on intermediate infrastructure before it enters the warehouse.DEFINED IN Where the transform sits
Euclid number: A number of the form (product of the first k primes) + 1.DEFINED IN Infinitude of primes
Euler characteristic: Vertices minus edges plus faces of any polyhedral division of a surface; 2 for a sphere, 0 for a torus.DEFINED IN Hairy ball theorem
Euler's disk: A heavy disk on a smooth surface, used to study this motion; also the name given to the phenomenon itself.DEFINED IN A spinning coin's last rattle
Euler's equations: The equations of motion for a rigid body's spin components in its own rotating frame.DEFINED IN Intermediate axis instability
Euphemism: A milder term substituted for one felt to be blunt, offensive or distressing.DEFINED IN Euphemism
Euphemism treadmill: Steven Pinker's term for the cycle in which each replacement acquires the connotations of its predecessor and is replaced in turn.DEFINED IN Euphemism
Eusociality: A social organisation with overlapping generations, cooperative brood care, and a reproductive division of labour into castes.DEFINED IN Sterile worker castes
Eutectic point: The lowest temperature at which a salt-water mixture can stay liquid, about minus twenty-one degrees Celsius for sodium chloride.DEFINED IN Freezing-point depression
Euthermic: At normal active body temperature.DEFINED IN Hibernation
Eutrophication: Enrichment of a water body with nutrients, raising primary production and, downstream of it, decomposition.DEFINED IN Coastal dead zones
Evaluation potential: The extent to which an individual's contribution can be identified within a group's total; the variable that carries most of the classic effect.DEFINED IN Social loafing
Evaluation set: A curated collection of cases with agreed correct outcomes, used to detect regressions.DEFINED IN Orchestration
Evaporator: The cold-side component where refrigerant absorbs heat.DEFINED IN How does a refrigerator cool food?
Evaporite: A rock formed where a body of seawater dried, locking its dissolved salts into the geological record.DEFINED IN Sea saltiness
Evapotranspiration: The transfer of water to the air from soil evaporation and plant transpiration, which consumes energy that would otherwise heat the air.DEFINED IN Urban heat islands
Event: A message reporting something that has already happened, addressed to nobody in particular and not refusable.DEFINED IN Commands and events · Event sourcing
Event as fact: A past-tense record that something occurred, as opposed to a command instructing a specific recipient to act.DEFINED IN The publisher that knows no subscribers
Event boundary: A point where the current model of the situation stops predicting well and is closed in favour of a new one.DEFINED IN Doorway effect
Event bus: A broadcast mechanism whose publishers and subscribers are unknown to each other, with no central place holding the interaction rules.DEFINED IN The middleman that reduces connections
Event history: The durable, ordered record of every result an execution received from outside itself.DEFINED IN Durable execution
Event horizon: The boundary beyond which nothing, not even light, can escape.DEFINED IN What is a black hole?
Event model: The working representation of the present situation, holding who and what is involved and what is underway, used to predict the next moment.DEFINED IN Doorway effect
Event sourcing: Treating an append-only record of events as the authoritative state, with all other stores derived from it.DEFINED IN Delivered versus retained
Event time: The timestamp recorded when something actually happened, carried in the event itself.DEFINED IN Event time versus arrival time
Event time / processing time: When a thing happened in the world, versus when the system learned of it; lateness is the gap between them crossing a closed boundary.DEFINED IN Late-arriving data
Event-based prospective memory: An intention retrieved on encountering an external cue.DEFINED IN Prospective memory
Event-carried state transfer: Publishing the full changed state with an event so subscribers need not call back for it.DEFINED IN Commands and events
Eventual consistency: The guarantee that replicas converge if writes stop, with no promise about when.DEFINED IN Replication lag · Separating the read model from the write model
Eviction policy: The rule deciding which entry is discarded when the cache is full, e.g. least-recently-used.DEFINED IN Caching
Evidential: A grammatical marker whose meaning is the speaker's source of information.DEFINED IN Grammatical evidentiality
Evidential burden: The movable obligation to respond once the other side has made its case credible.DEFINED IN Burden of proof
Evidential strategy: An optional lexical or constructional way of indicating source, as in English, without a closed paradigm.DEFINED IN Grammatical evidentiality
Evidentialism: The view that belief is justified only in proportion to the evidence supporting it.DEFINED IN Faith and evidence
Evocation: Behaviour that elicits from a partner the very response it anticipated, so the expectation is confirmed by evidence it created.DEFINED IN Adult attachment patterns
Excess volatiles: Substances such as water, carbon dioxide and chlorine present at the surface in far greater quantity than rock weathering could supply, taken to have been degassed from the interior.DEFINED IN Sea saltiness
Excess-of-loss layer: Cover of a stated limit above a stated attachment point, written "limit xs attachment".DEFINED IN Catastrophe reinsurance
Exchange argument: The proof technique of editing an arbitrary optimal solution to include the greedy choice without worsening it.DEFINED IN When the best step now is safe
Exchange entitlement: The set of food bundles an endowment can be converted into at prevailing wages and prices.DEFINED IN Famine amid plenty
Exchangeable aluminium: Soluble aluminium in acid soils that damages root tips; precipitating it is the main benefit of liming.DEFINED IN Lime-induced nutrient lockup
Exclusionary displacement: The households who would have moved into a district and can no longer afford to, invisible in any count of who left.DEFINED IN Gentrification
Exclusionary rule: The suppression of evidence obtained in breach of a constitutional or statutory limit on searches.DEFINED IN Exclusionary rule
Exec form: The start-command syntax that runs a binary directly rather than through a shell.DEFINED IN The first process
Execution error: A successfully delivered report that the requested work did not achieve its goal.DEFINED IN Protocol errors versus execution errors
Exercise-associated muscle cramp: Cramp occurring during or shortly after exertion, distinguished here from metabolic cramps with a measurable cause.DEFINED IN Muscle cramp
Existence disclosure: Learning that a document exists from counts, facets, timing, or error differences, without seeing its contents.DEFINED IN Permission-aware retrieval
Exit and voice: Hirschman's pair of responses to decline: leaving, or staying and pressing for change, where the first tends to remove the people best placed to do the second.DEFINED IN Who leaves first
Exit code 137: 128 plus signal 9, the conventional shell encoding for a process terminated by SIGKILL.DEFINED IN Killed with memory to spare
Exogamy: The rule that one must marry outside a defined group.DEFINED IN Cross-cousin marriage · Marrying outside the group
Exonym: A name for a place or people used by outsiders and not by the inhabitants themselves.DEFINED IN Exonyms
Expectancy effect: The tendency for a teacher's or student's belief about likely performance to influence actual performance; real but modest, and much argued over.DEFINED IN Ability grouping
Expectant category: Those whose injuries are judged unsurvivable given available resources, offered comfort care while others are treated.DEFINED IN Emergency triage
Expectation violation: The gap between how long an interval was expected to take and how long it took, which appears to drive the judgement more than the interval itself.DEFINED IN Return-trip effect
Expected harm: The size of a possible harm multiplied by the probability that one's act brings it about.DEFINED IN Imperceptible harms
Expected rank: An alternative objective scoring how far down the true ordering your pick fell, rather than only whether it was first.DEFINED IN Optimal stopping
Expected running time: The average over the algorithm's own random choices, holding the input fixed; not an average over inputs.DEFINED IN Shuffling before sorting
Expected value: The probability-weighted average outcome, measured in money; reliably negative for the buyer of any sustainable policy.DEFINED IN Insurance
Expected waiting time: For independent trials each succeeding with probability p, the mean number of trials to the first success is 1/p.DEFINED IN Completing a collection
Experience curve: The observed regularity that unit cost falls by a roughly constant percentage with each doubling of cumulative output.DEFINED IN Experience-curve pricing
Experience good: Something whose quality cannot be judged before purchase, only after consumption.DEFINED IN Landmark restaurants · Uninformative advertising
Experiencing self: The self that lives through each moment, whose totals nobody stores.DEFINED IN Remembered holidays
Explicit monitoring theory: The account that pressure directs attention to the mechanics of execution, disrupting automated skill.DEFINED IN Choking under attention
Exploration-exploitation: The trade-off between acting on current best estimates and gathering data that could improve them.DEFINED IN Recommendation narrowing
Explosion limit: A boundary across which carrier growth changes sign.DEFINED IN Chain-branching explosion limits
Exponential backoff with jitter: Retrying after a randomised, exponentially growing delay, so that clients neither hammer nor synchronise.DEFINED IN Retry storms
Exponential discounting: Shrinking value by a constant proportion per unit of time; the only rule that keeps preferences consistent as both options recede.DEFINED IN Delay discounting
Exponential growth: Growth by a constant factor per step, under which a large head start is worth only a fixed number of extra steps.DEFINED IN Paper folding limit
Exposure bias: The mismatch that results: the model is never trained on the self-generated prefixes it must continue from at inference.DEFINED IN One improbable word
Exposure effect: An impact that accumulates with time spent in a place, rather than arriving all at once on moving there.DEFINED IN Persistent poor neighbourhoods
Exposure problem: The risk of winning part of a needed combination at a price justified only by the whole, which drives bids down to stand-alone values.DEFINED IN Exposure problem in package bidding
Expressive language: The ability to produce speech, which lags comprehension in the second and third years.DEFINED IN Toddler tantrums
Expropriation risk: The chance an asset will be seized by those with power, which sets the return on any investment that cannot be moved.DEFINED IN Border prosperity discontinuity
Extended deterrence: Deterring an attack on an ally rather than on oneself, which requires a far larger claim to be believed.DEFINED IN Deterrence
Extended phenotype: The idea that a gene's effects include changes it causes in another organism's body or behaviour.DEFINED IN Parasite host manipulation
Extended statistics: Stored summaries over a group of columns together, capturing correlation the marginals cannot.DEFINED IN Query plan estimation
External connection pooler: A proxy such as PgBouncer or RDS Proxy multiplexing many client connections onto fewer real backend ones.DEFINED IN Connection exhaustion before CPU
External focus of attention: Directing attention to the movement's effect in the world rather than to the body producing it.DEFINED IN Choking under attention
External fragmentation: Free memory that cannot satisfy a request because every hole is smaller than the request.DEFINED IN Memory fragmentation
External storage function: The role of notes as a record to be studied later, as distinct from their effect at the moment of writing.DEFINED IN Note-taking by hand
Externality: A cost or benefit falling on someone outside the transaction, and therefore absent from its price.DEFINED IN Price signals
Extractable versus total: Two classes of soil test, one estimating what a root can reach and one the whole stock present; this problem is visible only in the difference.DEFINED IN Lime-induced nutrient lockup
Extraction: The write-time judgement about which statements are worth keeping.DEFINED IN What an assistant should forget
Extraneous load: Demand on working memory created by how material is presented rather than by what it contains.DEFINED IN Split attention in materials
Extravillous trophoblast: Fetal cells that invade the uterine lining and remodel its arteries.DEFINED IN Pregnancy immune tolerance
Extreme value: The maximum of a sample, which grows with sample size even when the underlying distribution is fixed.DEFINED IN Falling records
Extremeness aversion: The tendency to avoid the highest and lowest options in a set and choose a middle one.DEFINED IN The dish nobody orders
Eyeline match: Cutting from a character looking off-screen to what they are looking at, in the direction implied.DEFINED IN Continuity editing
Eyewall: The ring of deep thunderstorms surrounding the eye, where the inflowing air rises and the heat is released.DEFINED IN Hurricane intensification

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Face: The public self-image a person maintains in interaction, in Goffman's sense.DEFINED IN Indirect requests
Face space: The model in which a face is a point defined by its deviations from an average face.DEFINED IN Face recognition
Face-threatening act: An act that by its nature damages someone's face, such as a request, refusal or criticism.DEFINED IN Indirect requests
Facilitated diffusion: Transport in which a binding carrier raises the total flux while the free concentration stays low.DEFINED IN Leghemoglobin in root nodules
Facilitation: One component improving conditions for the other, as by fixing nitrogen or reducing wind.DEFINED IN Agroforestry overyielding
Facilitation, tolerance, inhibition: Connell and Slatyer's three ways early occupants can affect later ones: helping them, neither helping nor hindering, or actively suppressing them.DEFINED IN Ecological succession
Factor: A resident agent who holds, prices and sells a distant principal's goods on commission, with discretion over the terms.DEFINED IN Trade diasporas
Factorial (n!): The product n x (n-1) x … x 1, counting the orderings of n distinct objects.DEFINED IN Factorial explosion
Facultative anaerobe: An organism that can use oxygen but does not require it, which is why such organisms both tolerate the newborn gut and destroy its oxygen.DEFINED IN Gut colonization order
Fail closed / fail open: Denying, or allowing, when the decision point cannot be reached.DEFINED IN Deciding apart from enforcing
Fail fast: Returning an error immediately rather than waiting for a timeout, so the caller's resources are not held hostage.DEFINED IN Circuit breakers
Failure detector: A component that reports which peers it believes to have failed, necessarily with errors.DEFINED IN Dead or just slow?
Failure injection: Deliberately introducing a fault (instance termination, latency, error responses, network partition) to observe the system's real response.DEFINED IN Chaos engineering
Failure rate (hazard rate): The chance an item fails in the next interval given that it has survived until now.DEFINED IN Bathtub failure curve
Faint young Sun problem: The conflict between a substantially dimmer early Sun and the evidence for liquid water on the early Earth.DEFINED IN Silicate weathering thermostat
Faithfulness: Whether stated reasoning reflects the process that actually produced the answer.DEFINED IN Chain-of-thought · Retrieval-augmented generation
Faithfulness (groundedness): Whether each claim in the answer is supported by the retrieved context, judged against that context rather than against ground truth.DEFINED IN Evaluating retrieval separately
Fall line: The boundary between hard upland rock and soft coastal-plain sediment, marked by rapids or falls where rivers cross it.DEFINED IN Fall-line cities
Fallback: The defined behaviour when a call fails, times out, or returns something the system rejects.DEFINED IN Orchestration
False discovery rate: The expected proportion of false positives among the hypotheses declared significant, controlled by the Benjamini-Hochberg procedure.DEFINED IN Testing many questions at once
False positive: A positive result in someone who does not have the condition.DEFINED IN Screening false positives
False positive rate: The fraction of non-members reported present; here set entirely by bits per element and hash count.DEFINED IN Bloom filters · Guardrails
Falsifiability: Popper's criterion: a claim is scientific insofar as it forbids observable outcomes.DEFINED IN Scientific testability
Familiarity: A fast, contextless signal that something has been encountered before, carrying no details.DEFINED IN Deja vu
Family-wise error rate: The probability of at least one false positive across a defined family of tests.DEFINED IN Testing many questions at once
Fan-in: How many runs a single merge pass consumes at once; set by available memory divided by the per-run buffer size.DEFINED IN Sorting more than fits
Fan-out: One incoming request spawning many parallel sub-requests whose answers must all be collected.DEFINED IN Tail latency
Fan-out query: A query that must be sent to every shard because it does not constrain the shard key.DEFINED IN Sharding
Far transfer: Applying learning to a situation sharing only abstract structure with the training.DEFINED IN Transfer of learning · Unused curriculum
Fast mapping: Forming a rough, provisional meaning for a word after one or two exposures.DEFINED IN Child word learning
Faster-is-slower effect: The finding, modelled and experimentally reproduced, that above a certain desired speed flow through a bottleneck falls as urgency rises.DEFINED IN Crowd crush
Fatigue cracking: Cracking that develops from repeated loads well below the strength of the material, as damage accumulates.DEFINED IN Road cracking
Faucet theory: Entwisle and Alexander's account in which school supplies resources to all children equally and out-of-school time supplies them unequally.DEFINED IN Summer learning loss
Fault: A fracture along which blocks of rock can move.DEFINED IN Why do earthquakes happen?
Feasible region: The set of plans satisfying every constraint; for linear constraints, a convex polytope.DEFINED IN Corner solutions
Feature detection: Deciding what to use by asking whether a specific ability is present, rather than inferring it from an identity or release.DEFINED IN Capability negotiation
Feature flag: A runtime switch that lets code be deployed without its behaviour being active.DEFINED IN Deploying more to break less
Feature freeze: The agreed policy of halting feature releases in favour of reliability work once the budget is exhausted.DEFINED IN Error budgets
Feature selection: Deliberately discarding measurements that do not bear on the distinction being made, to keep them out of the distance.DEFINED IN Curse of dimensionality
Fechner's law: The logarithmic sensation scale obtained by treating successive just-noticeable differences as subjectively equal steps.DEFINED IN Just-noticeable difference
Federated governance: Rules agreed across domains and enforced by the platform, covering identifiers, privacy and documentation.DEFINED IN Federated data ownership
Fee shifting: A rule requiring one party, usually the loser, to pay part or all of the other's legal costs.DEFINED IN Loser-pays cost rules
Feed conversion ratio: Kilograms of feed per kilogram of animal produced, the farm counterpart of ecological efficiency.DEFINED IN Trophic cost of meat
Feed-forward block: The position-wise half of a transformer layer, holding most of its parameters.DEFINED IN Where a fact lives in a model
Feedback loop: The cycle in which the result of an attempt informs the next attempt; break it and repetition entrenches whatever you did.DEFINED IN Deliberate practice · Model drift
Feedforward: Correcting from a model of the disturbance before any error appears.DEFINED IN Feedback control
Feigned retreat: A deliberate withdrawal intended to draw an enemy into a disordered pursuit.DEFINED IN Feigned retreat
Fellegi-Sunter model: The 1969 probabilistic framework scoring field agreements by how informative each is, with two thresholds and a clerical review band between them.DEFINED IN Which record is the real one
Fencing token: A monotonically increasing number attached to writes so that a stale holder's writes are rejected.DEFINED IN Dead or just slow? · Distributed consensus · Split-brain
Fermat's little theorem: For prime p and a not divisible by p, a to the power p-1 leaves remainder 1 modulo p.DEFINED IN Compositeness without factors
Fermentation: Yeast consuming sugars and releasing carbon dioxide gas (and a little alcohol).DEFINED IN What makes bread rise?
Few-shot prompting: Including a small number of input-output examples in the prompt rather than describing the task.DEFINED IN Few-shot prompting · Prompt sensitivity
Fiat money: Money whose value rests on acceptance and authority rather than material.DEFINED IN Origin of money
Fibrocartilage: Repair tissue rich in type I collagen that fills a cartilage defect after marrow stimulation; mechanically inferior to the hyaline cartilage it replaces.DEFINED IN Cartilage healing
Fibrosis: The collagen-laying repair response that produces a scar.DEFINED IN Limits of regeneration
Fidelity vs accuracy: Whether a copy agrees with the target (including its errors) versus whether the copy is correct.DEFINED IN Copying something you can only question
Field capacity: The water a soil retains after free drainage stops, the wettest state a root zone normally sits in.DEFINED IN Irrigation scheduling depth
Field experiment: A trial run in a real market with real buyers, as opposed to a laboratory judgement task.DEFINED IN Charm pricing
Fighting hypothesis: The contested proposal that left-handedness persists in humans because it pays in physical conflict while rare.DEFINED IN Left-hander advantage
File carving: Recovering data by scanning raw storage for known file-format signatures rather than using filesystem metadata.DEFINED IN File deletion
Fill rate: The proportion of demanded units supplied from stock when asked for.DEFINED IN Safety stock · Stockout demand censoring
Filled pause: An audible hesitation such as uh or um, as opposed to a silent gap.DEFINED IN Filler words · Transcribed speech
Filter bubble: The claim that algorithmic curation seals users into narrow informational worlds; the mechanism is real, the measured magnitude is contested.DEFINED IN Recommendation narrowing
Final reserve: Fuel that must remain untouched on landing, defined as a period of holding flight rather than a quantity.DEFINED IN Contingency fuel
Fine-tuning: Further training of a pretrained model on a narrower corpus to shift its behaviour.DEFINED IN Fine-tuning versus retrieval · Foundation model economics
Fingerspelling: Representing the letters of a spoken language's alphabet on the hands; a borrowing device, not the language itself.DEFINED IN Sign language
Finite population correction: The factor √((N − n)/(N − 1)) reducing the standard error when the sample is a large fraction of the population.DEFINED IN Sample size versus population
Finite-time singularity: A solution in which a quantity diverges at a specific finite time rather than approaching a limit.DEFINED IN A spinning coin's last rattle
Fiqh: The jurists' fallible understanding of divine law, distinguished from the divine law itself.DEFINED IN Living interpretation of a fixed text
Fire sale: Forced selling into a market too thin to absorb it, realising a loss that holding would not have caused.DEFINED IN Bank runs
Firm price (lump sum): One figure for a defined scope, with the contractor carrying overruns inside it.DEFINED IN Quoting a job
Firm-specific human capital: Skill and knowledge valuable only inside one organisation, which raises internal value while lowering mobility.DEFINED IN Who leaves first
Firn: Compacted granular snow, partway to ice, still porous enough for air to circulate through it.DEFINED IN Ice core records
First-order elimination: Removal of a constant fraction of the drug present per unit time, which is what makes a half-life a fixed number.DEFINED IN Steady-state dosing
Fisher's principle: The argument that selection on parents drives investment in the two sexes to equality, because the rarer sex always yields more descendants per head.DEFINED IN Balanced sex ratios
Fisher-Muller effect: The advantage of recombination in bringing separately arisen beneficial mutations into one genome.DEFINED IN Cost of sexual reproduction
Fitness for purpose: The view that quality is judged relative to an intended use, not in the abstract.DEFINED IN Wrong with nothing missing
Fitness for use: The principle that quality is relative to a purpose rather than an absolute property of a dataset.DEFINED IN Grade earned, not declared
Fitting: The space designed into the sides of each letter, which decides how tightly words set.DEFINED IN Optical sizes in type
Fixed action pattern: A stereotyped, largely invariant behaviour released by a trigger rather than assembled afresh each time.DEFINED IN Contagious yawning
Fixed cost: Expenditure that continues whether or not the business trades: loan repayments, insurance, rates, licences.DEFINED IN Tourism seasonality
Fixed floor: The portion of a usage-based bill that accrues per hour of existence rather than per unit of work.DEFINED IN Metered cost
Fixed versus marginal cost: The one-off cost of building capacity against the per-use cost of exercising it.DEFINED IN Foundation model economics
Fixity check: Recomputing a checksum to confirm stored bits have not changed.DEFINED IN Digital preservation churn
Flaky test: A test whose pass or fail outcome varies without any change to the code under test.DEFINED IN The test pyramid
Flash translation layer: The firmware map from host logical addresses to physical locations, which makes out-of-place writing invisible.DEFINED IN Write amplification
Flash-spotting: Locating a gun by taking simultaneous bearings on its muzzle flash from separated observation posts.DEFINED IN Shoot-and-scoot artillery
FLC: FLOWERING LOCUS C, the Arabidopsis repressor whose stable silencing by cold constitutes the memory of winter.DEFINED IN Vernalization
Flicker fusion: The point at which an interrupted light stops appearing to flicker and looks steady.DEFINED IN Apparent motion
Flocculation: The clumping of fine clay particles on meeting salt water, which makes them settle much faster.DEFINED IN Silted harbours
Flow efficiency: The fraction of lead time during which the item was actively worked on.DEFINED IN Where the time actually goes
Flow separation: The point at which that layer stalls against rising pressure and detaches, leaving a wake.DEFINED IN Golf ball dimples · Magnus effect
Fluctuation theorem: A quantitative result giving the probability of short-lived, small-scale violations of the second law.DEFINED IN Irreversibility
Fluency illusion: Mistaking the ease of processing familiar material for evidence that it has been learned.DEFINED IN Retrieval practice
Flush: Sending the collected statements to the database, distinct from committing the transaction that contains them.DEFINED IN Collecting changes before committing them
Flutter: A self-excited oscillation in which the motion itself generates the force that sustains it, distinct from resonance with an outside rhythm.DEFINED IN Resonance
Flux pinning: The trapping of those filaments at material defects, which freezes the field configuration into a true positional trap.DEFINED IN Superconducting levitation
Flyby anomaly: Small unexplained velocity residuals observed in some Earth flybys, of order millimetres per second.DEFINED IN Gravity assist
Focal cue: A cue whose noticing is part of processing the ongoing task, which allows retrieval without monitoring.DEFINED IN Prospective memory
Focal point: The option a group converges on without communicating, because it stands out; the mechanism that runs backwards here.DEFINED IN Compromise capitals · Concert pitch standard
Focus: The underground point where rupture begins.DEFINED IN Why do earthquakes happen?
Fold-over: A second block of runs with all signs reversed, which separates main effects from two-factor interactions.DEFINED IN Confounded factorial effects
Folk etymology: Reanalysis of an opaque name into familiar words, which can then freeze into the spelling.DEFINED IN Place names
Fondaco / funduq / kontor: The walled compound of warehouse, lodging and hall granted to a foreign merchant community in a host city.DEFINED IN Trade diasporas
Food availability decline: The older explanation of famine as a fall in the aggregate food supply, which entitlement analysis shows to be neither necessary nor sufficient.DEFINED IN Famine amid plenty
Food miles: The distance a food travels from producer to consumer, used as a proxy for its environmental cost.DEFINED IN Food miles
Foraging / living off the country: Drawing supply from the land being crossed rather than from a base, which frees the army from the radius but binds it to the harvest.DEFINED IN Military logistics
Forbidden transition: An atomic decay slow enough to be suppressed by collisions, as with oxygen's red 630 nm line.DEFINED IN Aurora
Force density: The number of security personnel per unit of population or area, the usual planning currency for occupation.DEFINED IN Holding conquered ground
Force generation: The process of raising, training and equipping units to a state where they can be employed.DEFINED IN Training cadre bottleneck
Force of selection: How strongly selection acts on a trait, which falls with the age at which the trait is expressed.DEFINED IN Senescence
Forebulge: The ring of uplifted ground around a loaded region, formed by displaced mantle and subsiding as that material returns.DEFINED IN Isostatic rebound
Foreign key: A column referring to another table's key, replacing a repeated copy of that row's facts.DEFINED IN Normalization
Formal discipline: The old doctrine that difficult subjects strengthen general mental faculties.DEFINED IN Transfer of learning
Formal equivalence: A translation aimed at matching the source's wording and structure as closely as the target language allows.DEFINED IN Translation equivalence
Formal independence: A relational test used by governance codes: no employment, material contract, or close family tie to the firm.DEFINED IN Board independence
Formant: A resonance of the vocal tract, a band of frequencies the tube amplifies; the positions of the lowest few define the vowel.DEFINED IN Helium voice · Telephone bandwidth · Whistled languages
Formative assessment: Checking understanding during instruction in order to adjust it, rather than to grade it afterwards.DEFINED IN Tutoring versus class size
Formula: In Parry's sense, a group of words regularly used under the same metrical conditions to express a given essential idea.DEFINED IN Formulaic oral composition · Metrical verse · Oral tradition
Forward compatibility: The ability of existing consumers to tolerate data or calls produced by a newer version, usually by ignoring what they do not recognise.DEFINED IN Backward compatibility
Forward compatible: Previous code can read data written under the new schema; upgrade producers first.DEFINED IN Compatibility has a direction
Forward model: An internal predictor that turns a motor command into an estimate of the sensory consequences it will produce.DEFINED IN Self-tickling
Forwarding table: A router's list of address blocks paired with the next hop to use for each.DEFINED IN Internet packet routing
Fouling factor: A tabulated design allowance of extra surface area, not a prediction of any particular service.DEFINED IN Heat exchanger fouling
Fouling resistance: The extra thermal resistance a deposit adds, in series with the wall and the two film resistances.DEFINED IN Heat exchanger fouling
Foundation model: A model trained broadly at scale, intended to be adapted to many downstream tasks.DEFINED IN Foundation model economics
Founder crops: The small set of plants first domesticated in the Fertile Crescent, including wheat, barley, peas and lentils.DEFINED IN East-west diffusion
Four-dimensionalism (perdurantism): The view that objects persist by having temporal parts, so an object is extended through time as well as space.DEFINED IN Identity over change
Fractal dimension: A number, typically between one and two for a coast, describing how rapidly detail accumulates as scale decreases.DEFINED IN Coastline paradox
Fractionation factor (alpha): The ratio of isotope ratios between two phases at equilibrium; about 1.0098 for oxygen-18 between liquid and vapour near 20 degrees.DEFINED IN Rainfall isotope distillation
Fracture initiation: The starting of a crack, the step that requires concentrated stress.DEFINED IN Sharpness
Fracture propagation: The running of an existing crack, which needs far less force because the crack tip concentrates stress itself.DEFINED IN Sharpness
Fracture toughness (K-one-C): The value of K at which a crack in a given material becomes unstable and runs.DEFINED IN Leak-before-break
Fragile base class problem: The effect where an internal change in a parent class silently breaks subclasses that depended on its internal call structure.DEFINED IN Composition over inheritance
Fragmentation: Free memory broken into gaps too small to satisfy new requests, wasting capacity that is nominally available.DEFINED IN Software aging
Free jazz: Improvisation without a pre-agreed chord scheme, relying on other shared structure instead.DEFINED IN Jazz improvisation
Free rider: Someone who benefits from a good without contributing to its cost.DEFINED IN Compulsory taxation · Costly religious demands
Free volume: The packing shortfall a glass retains; not literal holes.DEFINED IN Physical ageing of plastics
Free-choice paradigm: The rate-choose-re-rate design later shown to produce apparent attitude change through a measurement artefact.DEFINED IN Cognitive dissonance
Free-fall arch: The region above the outlet where grains leave the load-bearing network and fall freely.DEFINED IN Hourglass flow rate
Free-riding: Supplying less effort because the benefit is shared while the cost is not.DEFINED IN Social loafing
Freedom of the trade: The right to practise a craft or trade in a town, granted by guild or corporation, usually on completing a term.DEFINED IN Apprenticeship indentures
Freeze frame: The snapshot of operating conditions recorded at the moment a code was set.DEFINED IN Misleading fault codes
Frequency response: How a system's output level varies across the range of pitches it passes.DEFINED IN Voice recording mismatch
Frequency seriation: Ordering deposits by the changing proportions of the types they contain.DEFINED IN Ceramic seriation
Frequency-dependent selection: Selection whose direction depends on how common a trait already is, and which therefore tends toward a stable mixture rather than fixation.DEFINED IN Balanced sex ratios
Freshness SLA: An agreed maximum lag between an event happening and it being visible in a table.DEFINED IN Grade earned, not declared
Fresnel reflection: The partial reflection that occurs at any boundary between optically different media, about four per cent for air and ordinary glass at near-normal incidence.DEFINED IN Night window reflections
Fresnel zone: The ellipsoidal region around the direct path that carries most of the signal energy; its radius grows with wavelength and distance.DEFINED IN Radio diffraction
Friction: Clausewitz's term for the accumulation of small difficulties that makes the simplest action in war hard.DEFINED IN Fog of war
Fried parameter (r₀): The diameter over which the incoming wavefront stays flat to about one radian; the effective aperture the atmosphere allows.DEFINED IN Atmospheric seeing limit
Friendship paradox: Feld's 1991 result that people's friends have, on average, more friends than they do.DEFINED IN Inspection paradox
Fringe: The alternating reinforcement and cancellation produced when two elements' signals are combined.DEFINED IN Radio interferometry
Fringing field: The part of the field that bulges beyond the electrodes, up through the glass, where a finger can reach it.DEFINED IN Capacitive sensing
Frisson: The shiver or gooseflesh some listeners report at particular musical moments, used in research because its onset can be timed precisely.DEFINED IN How can music create emotion?
Front region: The setting in which an activity is presented to an audience, in Goffman's sense.DEFINED IN Authenticity
Front-channel logout: The browser-mediated variant using hidden iframes; fragile where third-party cookies are blocked or partitioned.DEFINED IN Signing out everywhere
Frontier: The reached-but-not-yet-finalised nodes, held in a priority queue keyed by tentative distance.DEFINED IN Nearest first
Frost heave: Uplift of ground by ice lenses that grow at a freezing front, fed by water drawn through unfrozen films.DEFINED IN Patterned ground
Froude number: The ratio governing wave-making, which falls as a hull is made longer at the same speed.DEFINED IN Rowing crew scale
Fruit of the poisonous tree: Evidence discovered indirectly through an earlier illegality, and the question of whether it too is excluded.DEFINED IN Exclusionary rule
Full compatibility: Both directions hold, so rollout order does not matter.DEFINED IN Compatibility has a direction
Function (Propp): An act of a character defined by its role in the plot, the unit from which wonder tales are assembled.DEFINED IN Story shape
Function word: A word carrying grammatical relation rather than content: article, auxiliary, copula, preposition, relative pronoun.DEFINED IN Headlinese
Functional dependency: A rule that one set of columns uniquely determines another.DEFINED IN Normalization
Functional overreaching: A short-term deliberate overload followed by a rebound above baseline.DEFINED IN Overtraining
Functional region: An area delimited by the flows within it, such as commuting or patient travel, rather than by law.DEFINED IN Functional versus administrative regions
Fundamental frequency: The rate at which the vocal folds open and close, heard as the pitch of the voice.DEFINED IN Helium voice · Telephone bandwidth
Fundamental law of road congestion: Duranton and Turner's finding that vehicle-kilometres travelled rise roughly in proportion to lane-kilometres built.DEFINED IN Induced traffic
Fundamental theorem of linear programming: If a bounded linear programme has an optimum, some vertex attains it.DEFINED IN Corner solutions
Fungibility: The property that any unit of money is interchangeable with any other of the same amount.DEFINED IN Mental accounting
Furlong: A block within an open field, sharing soil and aspect, subdivided into parallel strips.DEFINED IN Scattered strip farming
Fusiform face area: A face-selective region strongly implicated in identity.DEFINED IN Face recognition · Pareidolia
Fusion of powers: The parliamentary arrangement in which the executive sits in the legislature and depends on its continuing confidence.DEFINED IN Why do democracies separate powers?
Föhn or chinook: A warm, dry downslope wind produced by exactly this crossing.DEFINED IN Rain shadow

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Gain: How large a corrective action is taken per unit of measured error.DEFINED IN Scaling that overshoots
Galactic algorithm: One whose asymptotic bound is superior but whose constants make it unusable at any practical input size.DEFINED IN Counting steps instead of timing
Galton's problem: That societies in a cross-cultural sample share history and borrowing, so are not independent observations.DEFINED IN Bridewealth and dowry
Galvanic series: The practical ordering of metals by corrosion potential in a specific electrolyte, such as seawater.DEFINED IN Sacrificial anodes
Gamma: The peak container acceleration divided by g; the dimensionless number that decides whether a shake fluidises the bed.DEFINED IN Brazil-nut effect
Garden of forking paths: Inflation of the error rate caused by data-dependent analysis choices, even when only one test is finally reported.DEFINED IN Testing many questions at once
Gas age-ice age difference: The gap between the age of a layer of ice and the age of the air trapped within it.DEFINED IN Ice core records
Gate: A check between chain steps that validates an intermediate result before it is allowed to propagate.DEFINED IN Prompt chaining
Gauge break: A change of rail track width at a frontier, forcing goods to be transhipped between wagons.DEFINED IN Landlocked disadvantage
Gelatinisation: The loss of starch's crystalline order when heated in water, which is what baking does to the granules.DEFINED IN Bread staling · What makes bread rise?
Gelifluction: Slow downslope flow of water-saturated soil over frozen ground, the directional process that turns circles into stripes.DEFINED IN Patterned ground
Gene flow: The movement of genes between populations by continued immigration, which can counteract local selection.DEFINED IN Island size rule
Genealogical bewilderment: A 1960s term for distress attributed to lacking knowledge of one's biological origins; a contested concept.DEFINED IN Adoption search
Generalised grievance: A complaint shared undifferentiated by all citizens, treated as a political rather than a judicial matter.DEFINED IN Standing to sue
Generalised pigeonhole principle: With N items in k boxes, some box holds at least N/k rounded up.DEFINED IN Pigeonhole principle
Generalization error: Expected error on new data drawn from the same distribution, which is what you actually care about.DEFINED IN Overfitting
Generalized exchange: An asymmetric marriage system in which wives circulate in one direction around a closed ring of groups.DEFINED IN Cross-cousin marriage
Generation time: The interval in which a bacterial population doubles; strongly temperature-dependent, and the quantity the whole risk turns on.DEFINED IN Buffet holding time
Generative processing: Learning activity that produces something new from the material, such as a paraphrase, summary or inference.DEFINED IN Note-taking by hand
Generic element: The part of a name giving the kind of place: by, ton, ceaster, thorp.DEFINED IN Place names
Genetic vulnerability: The exposure of a crop arising from widespread reliance on a narrow set of genotypes.DEFINED IN Monoculture fragility
Geometric mean: The *n*th root of a product, the correct per-round summary of compounding growth.DEFINED IN Time average versus ensemble average
Geometric mean index: Sqrt(n_glass), the coating index that makes the two reflected amplitudes equal.DEFINED IN Anti-reflective coating
Geometric similarity: The assumption that larger boats are scaled copies of smaller ones rather than differently shaped.DEFINED IN Rowing crew scale
Geostrophic balance: The state in which those two exactly oppose one another and the flow runs parallel to the isobars.DEFINED IN Geostrophic wind
Ghost entry: A remembered key whose data was evicted, used as evidence about a policy's recent mistakes.DEFINED IN Choosing what to forget
Gibrat's law: The assumption that a city's expected growth rate is independent of its current size; the engine that generates the rank-size shape.DEFINED IN Primate cities
Gift exchange: Transfer of goods or services in a form that creates or maintains a relationship rather than settling an account.DEFINED IN Gift obligation
Gist: The structure or regularity common to a set of experiences, as opposed to the details of any one of them.DEFINED IN Sleeping on a problem
Glacial isostatic adjustment (GIA): The ongoing deformation of the solid Earth in response to past ice loading and unloading.DEFINED IN Isostatic rebound
Glass transition: The temperature below which a material's molecules lose the mobility to rearrange, freezing the process in place.DEFINED IN Bread staling · Glass transition · Physical ageing of plastics · Rubber elasticity
Glaze: A thin, transparent, medium-rich paint layer applied over dried paint to modify its colour, often the last thing a painter does.DEFINED IN Varnish removal
Glazing rebate: The channel holding the pane's edge, drained through weep holes.DEFINED IN Setting blocks
Glen's flow law: The empirical relation that ice strain rate grows roughly as the cube of applied stress.DEFINED IN Glacier flow
Gliadin: The flour protein that supplies extensibility, the flow that lets dough stretch without tearing.DEFINED IN What makes bread rise?
Glider: A Life pattern reproducing itself one square diagonally every four generations.DEFINED IN Cellular automata
Global secondary index: An index spanning all shards, allowing lookups by a non-shard-key column at the cost of a shared structure to maintain.DEFINED IN Sharding
Global state: Mutable data reachable from anywhere in a program without being passed in, and therefore changeable from anywhere.DEFINED IN The singleton regret
Global warming potential: The warming from a mass of a gas relative to the same mass of carbon dioxide over a stated horizon.DEFINED IN Landfill methane
Glomerulus: A hub in the olfactory bulb where all sensory neurons expressing the same receptor type converge.DEFINED IN Smell coding
Gluten: The stretchy protein network in wheat dough that traps the gas.DEFINED IN What makes bread rise?
Glutenin: The flour protein that supplies elasticity, the resistance that makes dough spring back.DEFINED IN What makes bread rise?
Glutenin subunits: The storage proteins whose composition, set by the variety, governs dough strength independently of how much protein is present.DEFINED IN Yield and protein in wheat
Glycated haemoglobin: Glucose bound to haemoglobin, used clinically to integrate glucose exposure over roughly the red cell's recent lifespan.DEFINED IN Diabetic complications
Glycation: The slow, enzyme-free attachment of glucose to protein, maturing over years into stable cross-links.DEFINED IN Diabetic complications
Glymphatic system: A proposed route by which cerebrospinal fluid flushes waste from brain tissue, reported to be far more active in sleep.DEFINED IN Sleep
Goal accessibility: The heightened ease with which material related to an active goal comes to mind.DEFINED IN Unfinished tasks
Goal difference: Goals scored minus conceded across the group, a measure of margin rather than results.DEFINED IN Group-stage tiebreaks
Goal-directed control: Action selected because of the outcome it is expected to produce, and sensitive to that outcome's current value.DEFINED IN Habit formation
God object: A class that has accumulated so many responsibilities that it becomes the system's bottleneck for understanding and change.DEFINED IN The middleman that reduces connections
Golden path: A supported, opinionated, pre-wired route for a common task, chosen because it is easiest.DEFINED IN The paved road
Golden record: The constructed best view of an entity, assembled from several sources rather than selected from them.DEFINED IN Which record is the real one
Golgi tendon organ: A tension receptor at the tendon junction that inhibits them.DEFINED IN Muscle cramp
Good-faith exception: Admission of unlawfully obtained evidence where the officer reasonably believed the search was lawful.DEFINED IN Exclusionary rule
Goodhart's law: Once a measure is made a target, the pressure to move it degrades its usefulness as a measure.DEFINED IN Benchmark saturation · Teaching to the test
Goodput: Completed work that someone still wants, as distinct from throughput, which counts work regardless of whether the answer was still needed.DEFINED IN Backpressure · Congestion collapse
Gough-Joule effect: The warming of rubber on stretching and its cooling on release, and the rise of its retractive force with temperature.DEFINED IN Rubber elasticity
Grade compression: The bunching of awarded grades near the top of the scale, which removes the ability to distinguish rather than merely shifting the average.DEFINED IN Grade inflation
Grade-equivalent: An old score unit expressing performance as the grade level at which it is typical, and a poor unit for arithmetic on gaps.DEFINED IN Summer learning loss
Graded loading: Progressively increasing mechanical demand rather than removing or restoring it in a single step.DEFINED IN Tendon rehabilitation loading
Gradient: The list of slopes — one per weight — describing how the loss would change if each weight changed slightly.DEFINED IN How does a neural network learn?
Graduated autonomy: Granting an automated system different degrees of independent action per capability rather than one blanket setting.DEFINED IN Autonomy as a dial
Graduated licensing: A staged driving-permit system that restricts the conditions, such as night driving and teenage passengers, in which new drivers may drive.DEFINED IN Adolescent risk
Grain: The level of detail one row represents, which determines which breakdowns of a metric are legitimate.DEFINED IN The semantic layer · What one row stands for
Grain protein concentration: Protein mass as a share of grain mass, calculated as measured nitrogen multiplied by 5.7 for wheat.DEFINED IN Yield and protein in wheat
Grammaticalisation: The historical process by which lexical items erode into obligatory grammatical markers.DEFINED IN Grammatical evidentiality
Grandfathering: Permitting an existing practice under a rule written to prohibit new instances of it.DEFINED IN Equipment bans in sport
Grandmother hypothesis: The proposal that post-reproductive lifespan persists because provisioning grandchildren yields more descendants than continued childbearing.DEFINED IN Post-reproductive life
Granularity: How finely the operations are divided; coarse means few and broad, fine means many and narrow.DEFINED IN Tool granularity
Granulation tissue: The pink, vessel-rich provisional tissue that fills a wound during the proliferative phase.DEFINED IN Wound healing
Graviportal posture: The straight, columnar limb stance of very large land animals, which reduces the muscle force needed to resist collapse.DEFINED IN Land size limits
Gravitational fractionation: The slight downward enrichment of heavier gas molecules in the firn, corrected using nitrogen isotopes.DEFINED IN Ice core records
Gravitationally self-consistent calculation: A solution in which the ocean surface, the gravity field, and the deforming solid Earth are solved together rather than separately.DEFINED IN Sea level fingerprints
Grazing incidence: Light striking a surface at a shallow angle, where the reflected fraction rises steeply toward total.DEFINED IN Night window reflections
Grazing tolerance: The set of traits, such as low growth form or rapid regrowth from the base, that lets a plant survive repeated defoliation.DEFINED IN Grazing and grassland richness
Greedy decoding: Always taking the highest-probability next token; removes deliberate randomness but does not, on its own, guarantee identical outputs across runs.DEFINED IN Evaluation suites · Temperature
Greedy routing: Forwarding a message to whichever contact seems closest to the target, using only local information.DEFINED IN Small-world networks
Greedy-choice property: The guarantee that some optimal solution contains the locally best first choice.DEFINED IN When the best step now is safe
Green's law: The resulting scaling of amplitude with depth to the minus one quarter, for a long wave shoaling without breaking.DEFINED IN Tsunami shoaling
Grid-forming inverter: Power electronics that establish a voltage waveform and can emulate inertial behaviour, rather than following an existing grid.DEFINED IN Grid balancing
Gridlock: The state in which a perpetual issue can no longer be discussed at all without the same entrenched positions and hostility.DEFINED IN Proxy arguments
Griffith criterion: The condition for a crack to propagate, giving strength falling roughly as the inverse square root of flaw depth.DEFINED IN Fibre strength and flaws
Griffith flaw: A microscopic surface crack that concentrates applied stress at its tip and so sets the real strength of a brittle material.DEFINED IN Tempered glass
Ground delay program: An initiative that assigns inbound flights arrival slots and holds them at their origin to match a reduced acceptance rate.DEFINED IN Ground delay programs
Ground plane: The conducting sheet or radial system supplying an antenna's return path and its mirror image.DEFINED IN Antenna ground plane
Ground wave: A surface-following mode at low and medium frequencies, dependent on the conductivity of the terrain.DEFINED IN Radio diffraction
Ground-bearing slab: A concrete floor cast directly on the ground, and so thermally coupled to it.DEFINED IN Cold floors
Grounding: Constraining an answer to content actually present in the supplied passages.DEFINED IN Retrieval-augmented generation
Groundspeed: Speed relative to the ground: airspeed plus the motion of the air itself.DEFINED IN Asymmetric flight times
Group contingency: An arrangement in which a consequence depends on the behaviour of a group rather than an individual, as in the Good Behavior Game.DEFINED IN Small disruptions in a classroom
Group coordinator: The broker that tracks group membership and drives the rebalance state machine.DEFINED IN Why adding a worker stops the others
Growth factor: The multiplier applied to capacity on resize; any value above one preserves the bound, and the choice trades wasted space against copy frequency.DEFINED IN The occasionally expensive operation
Growth fraction: The proportion of cells in a tissue or tumour that are actively in the cell cycle at a given moment.DEFINED IN Chemotherapy selectivity
Grue: Goodman's predicate applying to things examined before a set time and found green, and otherwise to blue things.DEFINED IN Problem of induction
Guidance document: A statement of how an agency reads or will enforce a rule, issued without full rulemaking procedure and formally non-binding.DEFINED IN Regulatory ossification
Guidance fading: Systematically withdrawing support as expertise develops, from worked example to completion problem to unaided problem.DEFINED IN Expertise reversal
Guidance hypothesis: The account of motor learning in which frequent feedback is leaned on during practice at the cost of retention afterwards.DEFINED IN Feedback timing · Practice feedback
Guslari: South Slavic epic singers, accompanied on the gusle, whom Parry and Lord recorded in the 1930s.DEFINED IN Formulaic oral composition
Gustafson's law: The 1988 counterpoint that larger machines are used for larger problems, whose serial fraction is often smaller.DEFINED IN Vertical and horizontal scaling
Gutsherrschaft: An estate system in which the lord held judicial and administrative authority over his peasants, not merely landlord rights.DEFINED IN Second serfdom
Gyre: A basin-scale loop of wind-driven surface current, closed by Earth's rotation and the continents.DEFINED IN Ocean circulation
Gödel numbering: An encoding of symbols, formulas and proofs as numbers, letting arithmetic describe its own syntax.DEFINED IN Incompleteness

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Habitual control: Action triggered by a cue and insensitive to the current value of its outcome.DEFINED IN Habit formation
Habituation: The decline in response to a stimulus that has repeatedly proved harmless.DEFINED IN Experienced-worker injuries · Fading attraction · Habituation versus sensitization · Semantic satiation
Hadley cell: The tropical overturning circulation: rising near the equator, poleward aloft, descending near 30 degrees.DEFINED IN Desert latitudes
Haemagglutinin: The surface protein influenza uses to enter cells, the main target of protective antibody, and the part that drifts.DEFINED IN Original antigenic sin
Haemoglobin mass: The total quantity of oxygen-carrying protein in the blood, distinct from concentration.DEFINED IN Altitude training
Haemolysis: Destruction of red cells, releasing free haemoglobin and injuring the kidneys.DEFINED IN Blood compatibility
Haemolytic disease of the newborn: Destruction of fetal red cells by maternal IgG crossing the placenta, classically anti-D.DEFINED IN Blood compatibility
Haemostasis: The first phase of repair, in which bleeding is stopped by vessel constriction, a platelet plug, and a fibrin clot.DEFINED IN Wound healing
Haircut: The margin by which pledged collateral exceeds the cash advanced, expressed as a percentage of the collateral's value.DEFINED IN Overnight repo lending
Hale's polarity law: The rule that leading-spot polarity is fixed within a hemisphere for a cycle and reverses at the next.DEFINED IN Solar cycle
Half-life (T): The time for half a population to decay, ln2/λ, independent of the starting amount.DEFINED IN Radioactive half-life
Half-open interval: A convention in which the start instant belongs to a version and the end instant belongs to the next, so intervals partition time.DEFINED IN Point-in-time joins
Halo orbit: A large periodic path traced around a collinear Lagrange point rather than a position held at it.DEFINED IN Lagrange points
Hamming code: A family placing parity bits at power-of-two positions so the failing checks spell out the position of a single flipped bit.DEFINED IN Error-correcting codes
Hamming distance: The number of bit positions in which two codewords differ.DEFINED IN Error-correcting codes
Handicap: An adjustment applied to a competitor's result or starting position to equalise expected performance.DEFINED IN Handicapping
Handicap principle: Zahavi's proposal that signals stay honest because they are costly, formalised by Grafen and substantially revised since.DEFINED IN Conspicuous signals
Handoff cost: The working context lost when a task passes from one agent to another, plus the effort of reconstructing it.DEFINED IN Many agents, one task
Handshake: The opening exchange in which two parties establish the terms of everything that follows.DEFINED IN Capability negotiation
Hanger: A vertical rope or rod transferring deck load up to the main cable.DEFINED IN Suspension bridge cables
Haplodiploidy: A sex-determination system in which females develop from fertilised eggs and males from unfertilised ones.DEFINED IN Sterile worker castes
Happens-before: Lamport's partial order: within a process by program order, across processes by message send preceding receipt.DEFINED IN Clock synchronization
Hard-look review: Judicial scrutiny of whether an agency genuinely weighed the evidence and alternatives, not merely whether it followed the steps.DEFINED IN Regulatory ossification
Hardening: Surfacing or engineering a site so that heavy use causes little further damage.DEFINED IN Honeypot sites
Harmless torturers: Parfit's case in which each of a thousand agents contributes an imperceptible amount to each of a thousand victims' severe pain.DEFINED IN Imperceptible harms
Harmonic number: The sum 1 + 1/2 + … + 1/n, close to the natural logarithm of n plus 0.577.DEFINED IN Completing a collection
Harness: The surrounding program that parses model output, executes tools, and enforces limits.DEFINED IN The agent loop · Tool calling boundary
Hash flooding: A denial-of-service attack that supplies deliberately colliding keys to force worst-case behaviour.DEFINED IN Finding without searching
Hau: The Maori concept Mauss invoked to explain the compulsion to return a gift, and the most contested part of his account.DEFINED IN Gift obligation
Hawking radiation: The predicted faint thermal emission from a horizon; not yet observed.DEFINED IN What is a black hole?
Hawthorne effect: The change in behaviour caused by the act of observing it, which inflates directly observed compliance rates.DEFINED IN Hand hygiene compliance
Hazard rate: The probability that an item fails in the next interval given that it has survived to now; the quantity that decides whether age matters.DEFINED IN Preventive replacement
Head of navigation: The furthest point upstream that a given class of vessel can reach.DEFINED IN Fall-line cities
Head-of-line blocking: The halting of everything behind an item that cannot be completed, in any system that preserves order.DEFINED IN Poison messages · The noisy neighbour
Head-to-head: A mini-table built only from matches between the tied teams.DEFINED IN Group-stage tiebreaks
Headhaul and backhaul: The heavier and lighter directions of a trade lane; the rate gap makes empty returns affordable.DEFINED IN Empty container repositioning
Headless BI: A semantic layer that serves definitions to multiple front-end tools rather than being tied to one.DEFINED IN The semantic layer
Headline present: The convention of using the present tense to report an event that has already happened.DEFINED IN Headlinese
Headward erosion: The extension of a channel upslope at its head, chiefly by the retreat of steepened reaches.DEFINED IN River capture
Headway: The time between consecutive vehicles on a route.DEFINED IN Inspection paradox · Mixed-speed rail capacity
Healthy worker survivor effect: The bias created when the people who remain in a hazardous job are those it has not yet harmed.DEFINED IN Experienced-worker injuries
Heat anticipator: A small heater beside a mechanical thermostat's sensor, making it cut out early to offset lag.DEFINED IN Thermostat overshoot
Heat load: The thermal burden of clothing that blocks evaporative cooling, and the main limit on how long a posture can be held.DEFINED IN Chemical protective posture
Heat sink: A body large enough to absorb heat without appreciably warming, so it keeps drawing indefinitely.DEFINED IN Cold floors
Heat-affected zone: Parent metal beside the weld, never melted but heated enough to change its microstructure.DEFINED IN Delayed weld cracking
Heavy tail: A distribution whose probability of large values falls off slowly, as a power rather than exponentially.DEFINED IN Unstable averages · Why the average recovery time lies
Hedged request: A duplicate sent to a second replica after a short delay, with the first answer taken and the other cancelled.DEFINED IN Tail latency
Hedonic adaptation: The tendency for emotional responses to a durable change in circumstances to weaken over time.DEFINED IN Hedonic adaptation
Held-Karp algorithm: An exact dynamic-programming solution to the travelling salesman problem running in time proportional to n^2 x 2^n.DEFINED IN Factorial explosion
Held-out set: Cases deliberately excluded from the tuning loop, kept as an honest check against fitting to your own suite.DEFINED IN Evaluation suites
Heliacal rising: A star's first reappearance before dawn after a period of invisibility, used as an annual anchor in several ancient calendars.DEFINED IN Festival calendars
Helical (secondary) flow: The corkscrew circulation in a bend, outward at the surface and inward along the bed.DEFINED IN River meanders
Hepatic extraction ratio: The proportion of drug removed by the liver in a single pass through it.DEFINED IN First-pass metabolism
Herd immunity threshold: The immune fraction, 1 - 1/R0, above which sustained transmission cannot be maintained.DEFINED IN Herd immunity
Herding: Convergence on the same choice through observation of others rather than independent assessment.DEFINED IN Traveler herding
Heritability: The share of the variation in a trait across a population attributable to genetic variation; not the share of one person's trait caused by genes.DEFINED IN Sibling differences
Heritage language: A language learned at home that is not the dominant language of the surrounding society.DEFINED IN Heritage language loss
Heterogeneous nucleation: Formation of an embryo against a foreign surface, which lowers the barrier and is how nearly all real freezing begins.DEFINED IN Supercooling
Heterosis (hybrid vigour): The superiority of a cross over the average of its two parents.DEFINED IN Hybrid seed decline
Heuristic: A method that finds a good solution quickly without guaranteeing it is the best one.DEFINED IN Factorial explosion
Hexagonal architecture: Cockburn's ports-and-adapters arrangement (2005) in which every source dependency points inward toward the domain.DEFINED IN Dependency direction
Hexagonal market areas: The idealised tiling that results when circular ranges are packed to leave no gaps and no contested overlaps.DEFINED IN Town spacing
Hidden profile: A situation in which the information needed for the right answer is held by one member, and group discussion favours what everyone already shares.DEFINED IN Group projects
Hide's theorem: The result that an axisymmetric, frictional circulation cannot sustain an angular momentum maximum in the fluid's interior.DEFINED IN Venus superrotation
Hiding power: A paint layer's ability to conceal what lies beneath it, set by pigment-binder index contrast, particle size, and film thickness.DEFINED IN Emerging pentimenti
Hierarchical encoding: Storing places nested in larger regions, then inferring their relations from the regions'.DEFINED IN Wayfinding
High Salinity Shelf Water: The dense, near-freezing, salt-enriched water that accumulates on a polar continental shelf.DEFINED IN Sea-ice brine rejection
Higher-order vagueness: The vagueness of "borderline" itself, which regenerates the problem one level up.DEFINED IN Vagueness
Hindsight bias: The tendency, once an outcome is known, to see the path to it as obvious and the warning signs as conspicuous.DEFINED IN Blameless review
Hippocampal replay: The compressed re-firing during sleep of neural sequences that occurred during waking experience.DEFINED IN Sleep
Historic precedence (grandfathering): Entitlement to the same series next season by virtue of having operated it this season.DEFINED IN Airport slot grandfathering
Hit rate: The fraction of accesses served by the cache rather than the slower level below it.DEFINED IN Caching
Hiyal: Stratagems in Islamic law for reaching a result the letter permits, permitted by some schools and condemned by others.DEFINED IN Ritual legal fictions
HLA: Human leukocyte antigens, the surface proteins by which immune cells distinguish self from foreign tissue.DEFINED IN Organ allocation matching · Transplant rejection
HLA-G and HLA-E: Barely variable class I molecules that engage inhibitory receptors rather than provoking attack.DEFINED IN Pregnancy immune tolerance
HMAC: A keyed hash that proves the sender knew a shared secret and that the covered bytes are unaltered.DEFINED IN A notification you did not ask for
HNLC: High-nutrient, low-chlorophyll regions, where a micronutrient such as iron limits growth despite plentiful nitrate.DEFINED IN Ocean productivity
HNSW: Hierarchical navigable small world, a layered proximity graph searched greedily from sparse to dense.DEFINED IN Approximate nearest neighbour search · Permission-aware retrieval
Hold baggage screening: Machine examination of checked bags for prohibited items, a detection control distinct from reconciliation.DEFINED IN Baggage reconciliation
Hold point: A scheduled stop in a works programme past which no further work may proceed until an inspection is passed.DEFINED IN Rough-in inspection
Hold-up: Renegotiation forced on a party after it has sunk a specific investment, exploiting that its alternative is now worth little.DEFINED IN Hostage capital
Hold-up problem: The risk that a partner renegotiates opportunistically once you have sunk a specific investment, and the under-investment that anticipating it causes.DEFINED IN Boundaries of the firm · Landlocked disadvantage
Holding current: The minimum current that keeps a triggered TRIAC latched on.DEFINED IN LED dimmer incompatibility
Holiday paradox: An interval that feels fast while lived and long once remembered.DEFINED IN Sense of time
Home advantage: The systematic excess of home wins over away wins across a balanced fixture list.DEFINED IN Home advantage
Homeorhesis: The coordinated shift in nutrient partitioning that supports a physiological state such as lactation, as distinct from homeostasis.DEFINED IN Dairy cow energy balance
Homeostatic sleep pressure: The drive to sleep that accumulates with time awake and dissipates during sleep.DEFINED IN Teenage sleep phase
Homochirality: The observed fact that life uses overwhelmingly one mirror form of its amino acids and sugars.DEFINED IN Molecular handedness
Homogamy: Pairing within the same social category, such as class, religion or education level.DEFINED IN Similar partners
Homogeneous nucleation: Formation of a critical embryo from the liquid alone; in water it needs roughly -38 °C.DEFINED IN Supercooling
Homologous temperature: A material's temperature as a fraction of its melting temperature on the absolute scale.DEFINED IN Slippery ice
Homology: Similarity inherited from a common ancestor, such as the shared bone plan of tetrapod forelimbs.DEFINED IN Convergent evolution
Homonym: One name used for genuinely different concepts in different systems.DEFINED IN Six names for one field
Homophily: The tendency to form ties with people already similar to you, which produces clustering with no influence at all.DEFINED IN Divorce contagion
Homoplasy: Similarity not inherited from a common ancestor; convergence is its main cause.DEFINED IN Convergent evolution
Honeypot site: A location deliberately provided with access and facilities so that visitors concentrate there rather than dispersing.DEFINED IN Honeypot sites
Hop limit (TTL): A counter in each packet, decremented at every router, that discards packets caught in loops.DEFINED IN Internet packet routing
Horizon line: The line holding the vanishing points of all horizontal ground directions, at the height of the viewer's eye.DEFINED IN Linear perspective
Horizontal gene transfer: Movement of genes between living bacteria rather than from parent to offspring, by conjugation, transformation, or transduction.DEFINED IN How does antibiotic resistance develop?
Horizontal scaling: Adding machines and dividing work between them (scaling out).DEFINED IN Vertical and horizontal scaling
Horizontal-axis vortex: A rotating body of air whose axis lies flat, as proposed by Schmidt'sDEFINED IN Shower curtain drift
Hormesis: A reported beneficial response to a low dose of an agent harmful at high doses; real in some systems, contested and often overstated in general.DEFINED IN Dose-response
Host specificity: How narrow the range of species a pest or pathogen can feed on; the narrower it is, the more a rotation hurts it.DEFINED IN Crop rotation
Hostage: Something valuable a party puts at risk to make its own promise credible, since breaking the promise destroys it.DEFINED IN Brand advertising
Hot cognition: Decision-making under emotional or social arousal, where adolescent performance diverges most from adult performance.DEFINED IN Adolescent risk
Hot key: A single key whose request rate is large enough to saturate the partition that owns it.DEFINED IN Hot partitions
Hotelling competition: The model in which sellers positioned along a line each move toward their rival, converging at the centre.DEFINED IN Media sameness
Hotelling's model: Spatial competition on a line where firms choose location and customers buy from the nearer seller.DEFINED IN Retail clustering
HttpOnly: A cookie attribute that hides the value from page JavaScript, limiting what a cross-site scripting flaw can steal.DEFINED IN Continuity over a protocol with no memory
Hub: A table holding only a business key with its load time and source, so nothing descriptive can force it to change.DEFINED IN Built never to be rebuilt
Hubble tension: The unresolved disagreement between the ladder's expansion rate and the value predicted from the cosmic microwave background.DEFINED IN Cosmic distance ladder
Huffman coding: An optimal prefix code for a known symbol distribution, using whole bits per symbol.DEFINED IN Lossless compression
Human milk oligosaccharide: A milk sugar indigestible to the infant that selectively feeds particular gut bacteria.DEFINED IN Gut colonization order
Human-edible feed: The portion of an animal's diet that people could have eaten directly, and the only portion the trophic argument actually applies to.DEFINED IN Trophic cost of meat
Hung jury: A jury unable to reach the required agreement, producing no verdict.DEFINED IN Jury deliberation
Hungry gap: The late-spring interval when the previous harvest's stores are exhausted and nothing new is ready.DEFINED IN Festival calendars
Hybrid retrieval: Combining keyword and embedding rankings, since each is blind where the other sees.DEFINED IN Embedding space · Retrieval-augmented generation
Hydration: The reactions in which cement minerals dissolve and re-precipitate as hydrated products, consuming water chemically.DEFINED IN Cement hardening
Hydraulic limitation: The constraint on maximum height imposed by the difficulty of lifting water to the topmost leaves.DEFINED IN Forest height race
Hydrodynamic lubrication: Load carried by pressure a moving surface generates by dragging viscous fluid into a converging gap.DEFINED IN Oil film in bearings
Hydrophobic effect: The exclusion of non-polar substances by water's own network.DEFINED IN Soap cleaning
Hydrostatic bearing: One separated by externally pumped fluid, independent of speed.DEFINED IN Oil film in bearings
Hydrostatic equilibrium: The condition in which the pressure gradient at every depth supports the weight of the material above it.DEFINED IN Stellar hydrostatic balance
Hydrostatic pressure: Pressure in a fluid at rest, increasing with depth in proportion to density and gravity.DEFINED IN Buoyancy
Hydrothermal circulation: The flow of seawater down through hot ocean crust at mid-ocean ridges, which chemically alters it before returning it.DEFINED IN Sea saltiness
Hyperbolic discounting: Dividing value by one plus a rate times the delay: steep near the present, flat further out.DEFINED IN Delay discounting · Why do we procrastinate?
Hyperbolic excess speed: The speed a probe retains relative to a planet once effectively free of it; unchanged by the flyby.DEFINED IN Gravity assist
Hyperexcitability: A transient state in which an axon's membrane sits nearer its firing threshold than normal.DEFINED IN Pins and needles
Hyperstability: Catch rates staying high as a stock declines, because fish aggregate and technology improves.DEFINED IN Fishery collapse
Hyperthermia: A temperature rise without a raised set point, as in heatstroke.DEFINED IN Fever
Hypertrophy: An increase in muscle size through accumulation of contractile protein, as distinct from swelling.DEFINED IN Early strength gains
Hypervelocity impact: A collision fast enough that material strength is irrelevant and both bodies behave as fluids.DEFINED IN Orbital debris cascade
Hypervisor: The layer running guest operating systems on virtualised hardware, supplying the extra kernel boundary containers lack.DEFINED IN Isolation without a machine
Hypocapnia: An abnormally low arterial CO2 level, the state hyperventilation produces.DEFINED IN Breathing urge
Hypogene cave: One dissolved by water rising from depth, often by sulfuric acid rather than carbonic.DEFINED IN Cave formation
Hyponatremia: A plasma sodium concentration below roughly 135 millimoles per litre.DEFINED IN Exercise-associated hyponatremia
Hypotonic: More dilute than plasma, which is what sweat is, and why sweating alone raises rather than lowers plasma sodium.DEFINED IN Exercise-associated hyponatremia
Hypoxia: Dissolved oxygen below roughly 2 milligrams per litre, the conventional threshold at which mobile animals flee and sessile ones die.DEFINED IN Coastal dead zones
Hyrum's Law: The observation that with enough users, every observable behaviour of a system will be depended upon by somebody, whatever the documented contract says.DEFINED IN Backward compatibility · Dependency conflicts · Opaque cursors · Recovering what the business meant
Hysteresis: When removing a cause does not restore the earlier state, because the system has settled into a different one.DEFINED IN Fishery collapse · Scaling that overshoots · The occasionally expensive operation

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I-PASS: A structured handoff bundle used in hospitals, shown in a multi-site paediatric study to reduce medical errors and preventable adverse events.DEFINED IN Shift handover
Ice-albedo feedback: The self-reinforcing loop in which ice reflects sunlight, cooling its surroundings and favouring more ice.DEFINED IN Ice age triggers
Iconoclasm: The destruction of religious images, and the doctrinal position endorsing it.DEFINED IN Prohibition of images
Idempotence: The property that applying an operation many times has the same effect as applying it once.DEFINED IN Declaring the destination, not the route · Exactly once is a property of the pipeline · Idempotent operations · Losing it or doing it twice · Protocol errors versus execution errors · Two systems, one record
Idempotency: The property that running a job twice for the same period leaves the same result as running it once.DEFINED IN Backfilling a pipeline
Idempotency key: A stable event identifier recorded on first handling so repeats are ignored.DEFINED IN A notification you did not ask for · Durable execution · Idempotent operations
Idempotent apply: Writing a change in a way that produces the same result if applied twice, which is what makes replay safe.DEFINED IN Change data capture
Idempotent consumer: A consumer that produces the same result whether it processes a message once or many times.DEFINED IN The outbox
Idempotent producer: A client that numbers batches per partition so the broker can reject retried or out-of-sequence writes; the default in Kafka since 3.0.DEFINED IN Order within a slice
Idempotent rebuild: Re-running a stage over the same input and getting the same output, which is what makes a derived layer disposable.DEFINED IN Refinement stages
Identification: Supplying an identifier that names an account, with no evidence attached.DEFINED IN Three questions people treat as one
Identity map: A registry guaranteeing that a given stored entity is represented by exactly one in-memory object within a unit of work.DEFINED IN Collecting changes before committing them
Identity-affecting choice: A choice that changes which individuals come to exist, not merely how they fare.DEFINED IN Non-identity problem
Idioglossia: A private language said to be invented by twins; genuine cases are rare, and shared mispronunciation is the usual finding.DEFINED IN Twin language delay
IEEE 754: The standard defining binary floating-point formats and the rounding behaviour nearly all hardware implements.DEFINED IN Floating-point error
IgE: The antibody class of allergy, almost all of it bound to mast cells rather than circulating.DEFINED IN Allergy
Ignition: The self-reinforcing stage in which a flow erodes more sediment than it deposits, and so accelerates.DEFINED IN Turbidity currents
Ijtihad: Independent juristic reasoning to derive a ruling where the sources do not settle it.DEFINED IN Living interpretation of a fixed text
Ill-conditioned: Of a system, having a near-zero smallest singular value, so its solution has huge coefficients and is hypersensitive to the data.DEFINED IN Double descent
Illiquid vs insolvent: Unable to raise cash today at fair value, versus owing more than the assets are worth at any horizon.DEFINED IN Bank runs
Illusion of knowing: Mistaking the fluency of familiar text for the ability to reproduce or use it.DEFINED IN Learning by explaining
Illusory truth effect: The finding that repeated statements are judged more likely to be true, partly because repetition makes them easier to process.DEFINED IN Persistence of misinformation
Image manifest: The document listing an image's layers in order along with its configuration.DEFINED IN Layers are diffs
Immunisation: Prior experience of control that protects against later uncontrollable exposure.DEFINED IN Learned helplessness
Immunoparalysis: The profound suppression of immune function seen alongside inflammation in sepsis, and a common route to late death from a second infection.DEFINED IN Sepsis
Immutable infrastructure: An approach in which running systems are never modified in place but replaced from a rebuilt image.DEFINED IN Configuration drift
Impact analysis: The downstream traversal of that graph from a known fault, to enumerate what may also be wrong.DEFINED IN Lineage
Impartiality: Applying a mandate's rules equally to all parties, irrespective of who they are.DEFINED IN Peacekeeping mandates
Impedance mismatch: The structural disagreement between the object model and the relational model that any mapping layer must absorb.DEFINED IN Objects that do not know they are stored
Implementation inheritance: Acquiring a parent class's code and fields, as opposed to merely declaring conformance to its interface.DEFINED IN Composition over inheritance
Implementation intention: An intention re-encoded as a specific if-then link between a concrete situation and the act.DEFINED IN Prospective memory · Unfinished tasks · Why do we procrastinate?
Implementation-defined behaviour: A construct whose behaviour each implementation chooses and documents.DEFINED IN Undefined behaviour
Implicit regularisation: A preference for simpler solutions that comes from the optimisation procedure rather than from any penalty you wrote down.DEFINED IN Double descent
Impossible trinity: Fixed exchange rates, free capital movement, and independent monetary policy cannot all be had at once.DEFINED IN Currency peg collapse
Impressed current: Cathodic protection driven by an external power supply and an inert anode rather than a dissolving one.DEFINED IN Sacrificial anodes
Improper output handling: The OWASP category for acting on model output without validation; LLM02 in the 2023 list for LLM applications, LLM05 in the 2025 revision.DEFINED IN Output as untrusted input
Impulse: Force multiplied by the time over which it acts, equal to the momentum it removes.DEFINED IN Crumple zones
Impulse-response model: A description of training in which fitness and fatigue are separate exponential responses to load, fatigue larger but shorter-lived.DEFINED IN Training taper
Imputation: Filling in a missing record using administrative data or nearby units when no response can be obtained.DEFINED IN Census undercount
In-context learning: A model adapting its behaviour from the prompt alone, with no change to its weights.DEFINED IN Few-shot prompting
In-degree: The number of unsatisfied prerequisites a task still has; the counter Kahn's algorithm decrements.DEFINED IN Order from pairwise rules
Inattentional amnesia: The rival account that the object is perceived but not retained long enough to report.DEFINED IN Inattentional blindness
Inbred line: A population self-pollinated until nearly every gene carries two identical copies.DEFINED IN Hybrid seed decline
Inbreeding depression: Reduced fitness in the offspring of related parents, caused mainly by inheriting matching harmful recessive alleles.DEFINED IN Marrying outside the group
Incandescence: The emission of light by a body simply because it is hot; the source of a candle flame's yellow.DEFINED IN Candle wick
Incidental constraint: A limit imposed by the implementation of the day rather than by policy.DEFINED IN Recovering what the business meant
Incidental key: A cut pattern that opens a mastered lock without having been issued.DEFINED IN Master keying
Incidental word learning: Acquiring a word's meaning from encountering it in context rather than from being taught it.DEFINED IN Vocabulary gap widening
Inclination compass: A compass reading the dip angle of the field lines, distinguishing pole from equator rather than north from south.DEFINED IN How do birds know where to migrate?
Inclusive fitness: Reproductive success counted to include the effect an individual has on the reproduction of relatives, weighted by relatedness.DEFINED IN Post-reproductive life · Sterile worker castes
Incoherent addition: Summation of waves with unrelated phases; cross terms average away and power rises in proportion to the count.DEFINED IN Massed string sound
Income pooling: Combining partners' incomes into a common fund rather than keeping them identified.DEFINED IN Household money pots
Incongruity-resolution: The leading account of humour: a setup establishes one interpretation, the punchline conflicts with it, and amusement comes from the sudden discovery of a second interpretation that fits.DEFINED IN Explained jokes
Incremental model: A transformation that processes only new or changed partitions rather than rebuilding the full history.DEFINED IN Where the transform sits
Incubation: The improvement in solving a problem that follows a period of not working on it.DEFINED IN Sleeping on a problem
Indenture: The written apprenticeship contract, so called because the copies were cut apart along a jagged line so each could be matched to the other.DEFINED IN Apprenticeship indentures
Independence: The condition that one observation's error carries no information about another's.DEFINED IN Error cancellation in averages
Independence assumption: Combining selectivities by multiplication, valid only when the columns are uncorrelated.DEFINED IN Query plan estimation
Independent deployability: The ability to build, test, and release one component without changing or coordinating with any other.DEFINED IN The distributed monolith
Independent statement: One neither provable nor refutable from a given set of axioms.DEFINED IN Incompleteness
Independently deployable: The property that a component can be built, tested, and released without coordinating with another team; the working definition of a service boundary.DEFINED IN Splitting a system into services
Indeterminate progress indicator: A spinner or looping animation that signals activity without claiming a completion percentage.DEFINED IN Progress-bar estimates
Index: A signal whose reliability comes from a physical constraint rather than a cost, as body size constrains a call's pitch.DEFINED IN Conspicuous signals
Index (manifest list): A manifest naming one image manifest per platform, so a single reference serves several architectures.DEFINED IN Tags versus digests
Index (Peircean): A sign linked to its object by real causal connection rather than resemblance or convention; a footprint, a weathervane, a photograph.DEFINED IN Photographic evidence
Index (signalling): A signal whose reliability comes from being causally produced by the state it advertises, rather than from being expensive.DEFINED IN Blushing
Index of a zero: The whole number of turns the field makes as you walk once around a small loop enclosing it.DEFINED IN Hairy ball theorem
Index run: The fan-to-terminal path of highest total resistance, which sets the fan's pressure.DEFINED IN Air balancing
Indexicality: The property of standing in that causal relation, which is what distinguishes a photograph from a depiction.DEFINED IN Photographic evidence
Indifference condition: The equilibrium requirement that every action a player actually uses yields the same expected payoff.DEFINED IN Penalty aiming
Indirect (cross-side) network effect: Value to one group rises with the size of a different group on the same platform, as with console owners and game developers.DEFINED IN Network effects
Indirect measure: A later judgement on a related question, where minority influence typically shows up more strongly than on the original one.DEFINED IN Minority influence
Indirect prompt injection: Instructions planted in content the system later retrieves, so the attacker need not be present.DEFINED IN Output as untrusted input · Prompt injection
Indirect strategy: Pursuing a goal by arranging its causal conditions rather than aiming at the goal itself.DEFINED IN Self-defeating aims
Individual transferable quota: A durable, tradable right to a percentage share of the total allowable catch.DEFINED IN Race to fish under quota
Induced compliance: The design in which a person is led to act or speak against their own attitude, with the incentive varied.DEFINED IN Cognitive dissonance
Induced demand: The rise in travel that follows a fall in its cost, including trips shifted from other routes, times and modes as well as new ones.DEFINED IN Induced traffic
Induced drag: Drag arising as a by-product of generating lift, rising with the square of the weight supported.DEFINED IN Contingency fuel
Induced fit: The enzyme changing shape to close around the correct substrate.DEFINED IN Enzyme specificity
Induced siphonage: Loss of one fixture's seal caused by a different fixture discharging past it in a shared stack.DEFINED IN Dry drain trap
Induced surface charge: Charge redistributed onto a conductor's surface by an external field, whose own field cancels the applied one inside the metal.DEFINED IN Faraday cage
Induced traffic: The separate, demand-side effect in which added capacity generates additional trips.DEFINED IN Phantom traffic jams
Infant mortality: The early period in which the failure rate of a population falls as defective units are eliminated.DEFINED IN Bathtub failure curve · Failure after repair · Warranty timing
Inference: Filling a gap the writer left unstated, using knowledge retrieved from memory rather than information on the page.DEFINED IN Knowledge and comprehension
Inferior alveolar nerve block: A dental injection at the mandibular nerve trunk, remote from the tooth being treated.DEFINED IN Local anaesthetic failure
Infiltration: Uncontrolled air exchange through gaps in the building envelope, distinct from conduction through the fabric.DEFINED IN Home insulation · Trail braiding
Infiltration capacity: The maximum rate at which a soil surface can take in water, distinct from how much it can hold.DEFINED IN Runoff from dry ground
Infiltration-excess overland flow: Runoff generated because rain outpaces the surface, as opposed to because the soil is already full.DEFINED IN Runoff from dry ground
Influence mine: One triggered by a passing ship's magnetic, acoustic or pressure signature rather than by contact.DEFINED IN Mine warfare
Information asymmetry: A situation where one party to a trade knows materially more than the other, which can prevent prices from sorting quality.DEFINED IN Price signals
Information cascade: A situation in which people rationally ignore their own information because the observed choices of others outweigh it, so their own choices stop conveying information.DEFINED IN Traveler herding
Information content (surprisal): How unexpected a word is given its context, measured as the negative logarithm of its probability there.DEFINED IN Word length
Information hiding: Parnas's principle of drawing module boundaries around the decisions most likely to change, so volatility stays private.DEFINED IN Coupling
Information structure: The packaging of a sentence into what is already known and what is new, which free-order languages often signal by position.DEFINED IN Word order
Informational influence: Treating others' judgements as evidence and genuinely updating one's belief.DEFINED IN Conformity
Infrared reflectography: An imaging technique using infrared light, which many paints transmit, to reveal underdrawing and buried changes.DEFINED IN Emerging pentimenti
Inglis solution: The 1913 elastic result for an elliptical hole, giving Kt as one plus twice the root of depth over tip radius.DEFINED IN Stress concentration
Inhibitory control: The ability to withhold a prepared response, one of the executive functions that matures slowly through the preschool years.DEFINED IN Toddler tantrums
Init duration: The separately reported portion of a cold start spent running your own initialisation code.DEFINED IN Cold starts
Initial-value problem: A prediction whose answer depends on knowing the system's present state; weather forecasting.DEFINED IN Forecast horizon
Initiation, propagation, termination: The three phases of a chain reaction: starting one chain, extending it, ending it.DEFINED IN Instant glue
Initiative boundary: The line in a system marking which side may begin an action, as opposed to which side holds the data.DEFINED IN Control as a classification
Injection ice: A massive ice body formed where pressurised water is forced into a space and freezes there.DEFINED IN Pingo growth
Injury in fact: A concrete, particularised harm to the claimant, actual or imminent, as distinct from a general interest in lawful government.DEFINED IN Standing to sue
Injury time: Discretionary added time at the end of a football half, decided by the referee.DEFINED IN Home advantage
Inlining: Folding a shared function back into its callers, the usual first step in undoing a premature abstraction.DEFINED IN When removing duplication hurts
Innate behavior: Behavior present from birth rather than learned.DEFINED IN How do birds know where to migrate?
Inode: The filesystem record holding a file's metadata and the list of blocks containing its contents.DEFINED IN File deletion
Inorganic phosphate: A by-product of energy turnover in the fibre, and a leading candidate for the direct cause of force loss.DEFINED IN Forearm pump in climbing
inputSchema: The schema a tool publishes describing the arguments it accepts.DEFINED IN A schema read by two audiences
Inquisitorial procedure: A system in which the court itself investigates and gathers evidence, as distinct from an adversarial trial between two parties.DEFINED IN Witch-hunt cascades
Insert-only modelling: Never updating or deleting a row, so change is recorded as a new version and history is automatic.DEFINED IN Built never to be rebuilt
Inside view: A forecast built from the specifics of the plan at hand.DEFINED IN Planning fallacy
Installed base: The existing stock of products, parts and skills built around a standard, and the main source of its inertia.DEFINED IN Technical standards
Institutional lock-in: The way training, promotion and procurement convert a chosen doctrine into commitments that outlast the argument for it.DEFINED IN Doctrine lag
Institutional memory: The accumulated record of why existing arrangements are as they are, held by long-serving participants rather than in documents.DEFINED IN Term limits
Instruction hierarchy: Training a model to give precedence to instructions from more privileged sources over those appearing in supplied content.DEFINED IN Delimiters as a boundary · System prompt priority
Instruction tuning: Fine-tuning on demonstrations of following instructions, which improves but does not remove phrasing sensitivity.DEFINED IN Prompt sensitivity
Instruction-data confusion: The absence of any enforced boundary between text meant as a command and text meant as material.DEFINED IN Prompt injection
Insular dwarfism: The evolution of markedly smaller body size in an island population.DEFINED IN Island size rule
Insular gigantism: The evolution of markedly larger body size in an island population, typically after release from predation.DEFINED IN Island size rule
Insulin-gated uptake: Glucose entry through a transporter that reaches the cell surface only under insulin's direction, as in muscle and fat.DEFINED IN Diabetic complications
Intaglio: Any printing method in which the ink sits in recesses below the plate surface, which is wiped clean before printing.DEFINED IN Drypoint burr
Integral windup: Error accumulated while the actuator is saturated, leaving an oversized total that must unwind before the loop recovers.DEFINED IN Feedback control
Intention to treat: Analysing every patient in the arm they were allocated to, preserving the randomisation despite non-adherence.DEFINED IN Randomized trials
Inter-token latency: The interval between successive output tokens, i.e. the streaming pace.DEFINED IN Time to first token
Interbout arousal: The periodic rewarming to normal temperature between torpor bouts, which consumes most of the winter's energy.DEFINED IN Hibernation
Intercalation: Inserting an extra day or month to keep a calendar aligned with the sky.DEFINED IN Calendar drift
Interchange fee: The charge a merchant's bank pays the card issuer per transaction; the source of most co-brand revenue, and capped in some jurisdictions.DEFINED IN Frequent-flyer currency
Interdiction: Attacks on movement routes rather than on forces, aimed at lowering the enemy's rate of arrival.DEFINED IN Amphibious buildup
Interior lines: The position of a force that can shift troops across shorter internal routes than its opponent must travel around the outside.DEFINED IN Defender's advantage
Interleaved practice: Alternating between types within a session, so consecutive items differ.DEFINED IN Interleaved practice
Intermediate disturbance hypothesis: The proposal that diversity peaks at moderate disturbance; influential, and substantially contested as a general theory.DEFINED IN Grazing and grassland richness
Intermediate value argument: The observation that a continuous quantity going from negative to positive must be zero somewhere between.DEFINED IN Wobbly table
Internal desynchrony: The state during a phase shift in which different organs and tissues have shifted by different amounts.DEFINED IN Shift work
Internal fragmentation: Unused space inside an allocated block, typically from rounding up to a size class.DEFINED IN Memory fragmentation
Internal resistance: The battery's own opposition to current, which rises as it cools and as itDEFINED IN Night-time alarm chirp
Internal working model: Bowlby's term for an accumulated expectation about others' availability and responsiveness, carried into new relationships.DEFINED IN Adult attachment patterns · Attachment
Interoception: The sensing and representation of the body's internal state, distinct from the senses directed outward.DEFINED IN Interoception
Interoceptive accuracy: Objective performance on a body-detection task; the measure whose validity is most contested.DEFINED IN Interoception
Interoceptive sensibility: Self-reported tendency to notice and attend to bodily sensations, measured by questionnaire.DEFINED IN Interoception
Interocular swap: Exchanging the two images between the eyes mid-experiment, used to test whether the competition is between eyes or between stimulus representations.DEFINED IN Binocular rivalry
Interpolation threshold: The capacity at which a model can just exactly fit its training data; where the double-descent peak sits.DEFINED IN Double descent
Interposition: Standing a force between the parties along an agreed line, making crossings costly for both.DEFINED IN Peacekeeping mandates
Intersection semantics: The rule that only capabilities present in both declarations may be used.DEFINED IN Capability negotiation
Intertropical Convergence Zone: The belt where the two hemispheres' trade winds meet and air rises, producing the tropical rain band; it migrates seasonally.DEFINED IN Monsoon
Interval cancer: A cancer that arises and becomes symptomatic between two scheduled screens.DEFINED IN Overdiagnosis
Intraplate earthquake: One occurring far from a plate boundary, where the loading mechanism is poorly understood.DEFINED IN Why do earthquakes happen?
Intrinsic carrier concentration: The density of mobile electrons and holes in an undoped semiconductor, about ten to the tenth per cubic centimetre for silicon at room temperature.DEFINED IN Semiconductor doping
Intrinsic dimension: The number of coordinates genuinely needed to describe where the data lies, usually far below the number measured.DEFINED IN Curse of dimensionality
Introsort: Musser's hybrid that starts as quicksort and falls back to heapsort past a depth limit, giving a true n log n worst case.DEFINED IN Shuffling before sorting
Invalidation: The discarding of a cached result because its key no longer matches, which cascades to every downstream step.DEFINED IN Build cache geometry · Caching
Invariance: A representation that stays stable when viewpoint or lighting change.DEFINED IN Face recognition
Invariant: A condition the code assumes to hold at a given point; its violation indicates a defect rather than an input problem.DEFINED IN Failing fast · Guardrails · Halving the haystack
Inverse document frequency: The weight given to a term for being rare across the corpus, which is what makes an identifier decisive in lexical scoring.DEFINED IN Hybrid search
Inverse fourth-power law: Scattering rising as the fourth power of one over the wavelength; a 1.75-fold gap becomes a ninefold one.DEFINED IN Why is the sky blue?
Inverted index: A structure mapping each term to the list of documents containing it, the reverse of the natural document-to-term direction.DEFINED IN Search indexing
Investment: The close encirclement of a place, which fixes the besieging army in position and starts the clock.DEFINED IN Siege camp attrition
Involuntary musical imagery (INMI): The research term for hearing music in the mind without having chosen to; earworm is the common name.DEFINED IN Earworms
Iodine value: A standard measure of how unsaturated an oil is, and the best single predictor of how readily it will cure.DEFINED IN Cast-iron seasoning
Ionisation: The stripping of electrons from atoms; the light of a meteor trail comes largely from those electrons recombining.DEFINED IN Meteor streaks
Ionospheric delay: The slowing of the signal by charged particles in the upper atmosphere,DEFINED IN How does GPS find your location?
Irreducible: Every state reachable from every other, which makes the stationary distribution unique.DEFINED IN Long-run chain behaviour
Ischaemia: An inadequate blood supply to a tissue, and so an inadequate oxygen supply.DEFINED IN Pins and needles
isError flag: The field in a tool result that marks the returned content as a failure report rather than a normal outcome.DEFINED IN Protocol errors versus execution errors
Island rule: The tendency for large-bodied lineages to become smaller and small-bodied lineages larger on islands.DEFINED IN Island size rule
ISM band: A frequency range reserved for industrial, scientific and medical use, which is why ovens run at 2.45 gigahertz.DEFINED IN Selective heating
Isobar: A line joining points of equal atmospheric pressure on a chart.DEFINED IN Geostrophic wind
Isohaemagglutinin: The naturally occurring anti-A or anti-B antibody present without prior transfusion.DEFINED IN Blood compatibility
Isohydric and anisohydric: Contrasting strategies that hold leaf water potential nearly constant, or let it fall while gas exchange continues.DEFINED IN Midday stomatal closure
Isolate: A lightweight sandbox within a shared runtime process, as used by V8-based platforms.DEFINED IN Cold starts · Isolates, containers, and startup cost
Isolated forearm technique: A tourniquet applied before the muscle relaxant, leaving one hand free to signal during surgery.DEFINED IN General anaesthesia
Isometric contraction: A contraction producing force without changing length, as in holding a grip.DEFINED IN Forearm pump in climbing
Isostasy: The buoyant balance in which the crust floats at a depth set by the weight it carries.DEFINED IN Isostatic rebound
Isothermal collapse: Contraction during which radiation carries the released energy away fast enough that the temperature hardly changes.DEFINED IN Star formation
Issuer (iss): The claim naming the party that minted the token.DEFINED IN A valid token in the wrong place
Item analysis: Examining how each option was chosen across ability levels, to judge the item rather than the students.DEFINED IN Diagnostic distractors
Item response theory: Models estimating a parameter for each item and each candidate, letting forms be linked through shared items.DEFINED IN Exam equating
Iteration cap: A hard limit on loop turns, the usual defence against a run that never terminates.DEFINED IN The agent loop

J

J-curve: Davies's pattern of sustained improvement followed by sharp reversal, opening a gap between expectation and reality.DEFINED IN Revolution timing
Jailbreak: Persuading a model to breach its provider's own policy, as distinct from subverting an application's instructions.DEFINED IN Prompt injection · Talked out of its own rules
Jamais vu: The inverse experience, in which something genuinely well known feels alien.DEFINED IN Deja vu
Jamming: The point at which sheared yarns crowd together and can rotate no further, after which the cloth stiffens sharply.DEFINED IN Bias-cut cloth · Shear-thickening food pastes
Janssen effect: The saturation of vertical stress with depth in a granular column, because wall friction carries the extra weight.DEFINED IN Hourglass flow rate
Janzen-Connell effect: Distance- and density-dependent seedling mortality near a conspecific adult, displacing successful recruitment away from the parent.DEFINED IN Janzen-Connell seedling mortality
Jeans criterion: The threshold mass above which a gas clump's gravity overcomes its pressure, rising with temperature and falling with density.DEFINED IN Star formation
Jet stream: A narrow band of fast west-to-east wind near the top of the troposphere, formed where the latitudinal temperature gradient is sharpest.DEFINED IN Asymmetric flight times
Job competition model: Thurow's framing in which education fixes a worker's position in a queue for jobs rather than their productivity in one; the rival account, human capital, holds that education raises earnings by raising what a worker can do.DEFINED IN Credential inflation
Jockeying: Switching lanes mid-wait, a behaviour that exists only because parallel queues do.DEFINED IN Single-queue service
Join depth: The number of sequential joins a query must resolve to reach an attribute.DEFINED IN The untidy shape that answers faster
Joint stiffness factor: The share of an external load that raises bolt tension, set by the ratio of bolt to member stiffness.DEFINED IN Bolt preload
Joukowsky equation: The pressure rise from a sudden velocity change, equal to density times wave speed times the change in velocity.DEFINED IN Water hammer
JSON Schema: A vocabulary for describing the shape of JSON data, used both to validate documents and to describe interfaces.DEFINED IN A schema read by two audiences
JSON-RPC 2.0: The remote-call convention underlying several modern protocols, which distinguishes a result from an error object in every response.DEFINED IN Protocol errors versus execution errors
Judgement of learning: A learner's prediction of how well they will later remember material just studied.DEFINED IN Fluency illusion
Judicial review: Examination of government action for compatibility with higher law — widespread, but not a feature of every democracy.DEFINED IN Why do democracies separate powers?
Just culture: A framework distinguishing honest error, at-risk behaviour, and reckless behaviour, applying different responses to each.DEFINED IN Blameless review
Just-noticeable difference: The smallest change in a stimulus an observer can reliably detect, measured against a given standard.DEFINED IN Just-noticeable difference

K

k-anonymity: A release condition requiring every quasi-identifier combination to be shared by at least k records.DEFINED IN Re-identification of anonymized data
k-factor: The position of the neutral axis expressed as a fraction of sheet thickness measured from the inside face.DEFINED IN Bend allowance
Kamacite: The nickel-poor, body-centred-cubic phase that grows as plates out of taenite on cooling.DEFINED IN Widmanstatten pattern
Kaplan-Meier estimator: The product over event times of (1 − deaths/at-risk), giving a survival curve from censored data.DEFINED IN Censored follow-up
Karst: The landscape produced by soluble rock: caves, sinkholes, springs and underground drainage.DEFINED IN Cave formation
Katabatic wind: A downslope flow driven by the negative buoyancy of surface-cooled air, rather than by a synoptic pressure pattern.DEFINED IN Katabatic winds
Kelly criterion: The bet size maximising the time-average growth rate, found by maximising expected log wealth.DEFINED IN Time average versus ensemble average
Kelvin wave: A coastally trapped wave held against a boundary by rotation, decaying in amplitude away from that coast.DEFINED IN Amphidromic points
Kelvin-Helmholtz timescale: How long gravitational contraction alone could sustain a star's luminosity; about thirty million years for the Sun.DEFINED IN Stellar hydrostatic balance
Kessler syndrome: The condition in which debris production by collisions exceeds removal, so the population grows without further launches.DEFINED IN Orbital debris cascade
Key salting: Appending a random suffix to a hot key so its writes spread across several partitions, at the cost of fan-out reads.DEFINED IN Hot partitions
Key stretching: Deliberately inflating the work needed to turn a password into its stored form, raising the cost of each guess.DEFINED IN Deliberately slow password checks
Key-value memory: The reading of a feed-forward block as matching input patterns and adding associated outputs.DEFINED IN Where a fact lives in a model
Keyset pagination: Resuming after a named sort key, so insertions and deletions before that key do not shift the boundary.DEFINED IN Opaque cursors
Keystone species: One whose effect on community structure is large relative to its abundance.DEFINED IN Keystone species
Kill chain: The sequence a weapon must complete, typically find, track, engage and hit, each link of which is a candidate for disruption.DEFINED IN Fading advantage of a new weapon
Kill switch: An operational flag kept indefinitely so an expensive or fragile subsystem can be turned off under load.DEFINED IN Feature flags
Kin investment: Resources, time and care directed toward relatives, expected to scale with relatedness and with confidence in it.DEFINED IN Grandparent asymmetry
Kinetic growth metamorphism: Crystal growth fast enough to preserve flat facets, driven by a temperature gradient.DEFINED IN Depth hoar in snowpack
Kinetic inertness: Slowness to exchange ligands, a property of rate and quite separate from where the equilibrium sits.DEFINED IN Chelate effect
Kingman's formula: An approximation giving mean waiting time as a variability term times a utilisation term times the mean service time.DEFINED IN Border queue surges
Kleiber's law: The empirical relation that basal metabolic rate scales roughly as body mass to the three-quarter power.DEFINED IN Metabolic scaling
Knowledge of results: Externally supplied information about the outcome of an attempt, distinct from the sensory information the attempt itself produces.DEFINED IN Practice feedback
Known unknown: A question you have identified but not answered.DEFINED IN Writing down what you could not determine
Known-value item: A product whose price a large share of shoppers can recall, and which retailers therefore price competitively as a signal.DEFINED IN Unit-price inversion
Komi: In Go, compensation points given to the second player to offset the first player's advantage.DEFINED IN Handicapping
Konzo: A sudden, permanent spastic paralysis of the legs associated with heavy intake of insufficiently processed bitter cassava alongside a protein-poor diet.DEFINED IN Cassava processing
Korte's laws: The empirical relationships between interval, separation and intensity that determine which apparent-motion percept occurs.DEFINED IN Apparent motion
KV cache: The stored attention keys and values for a sequence, which let each new token attend to earlier ones without recomputation, and which consume memory in proportion to batch size and context length.DEFINED IN Batching and the throughput trade · Context window · Prefill and decode

L

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Label space: The set of answers the examples show as permissible, which examples communicate implicitly.DEFINED IN Few-shot prompting
Labour market tightness: The ratio of vacancies to unemployed workers, which governs how quickly each side finds the other.DEFINED IN Vacancies alongside unemployment
Lactational amenorrhoea: The suppression of ovulation by frequent suckling, which delays the next conception.DEFINED IN Infant night waking
Lactic acid bacteria: The acid-producing bacteria that dominate a sourdough starter, mostly Lactobacillus and its relatives.DEFINED IN Sourdough stability
Lag effect: The finding that among spaced schedules, longer gaps generally produce better long-term retention, up to the point of retrieval failure.DEFINED IN Spacing effect
Lake Wobegon effect: The finding that nearly all US states reported above-average pupils, named for the fictional town where every child is above average.DEFINED IN Teaching to the test
Lambert's cosine law: The rule that a matte surface's brightness follows the cosine of the angle between its facing direction and the incoming light.DEFINED IN Stage lighting angle
Land equivalent ratio: The sum, across components, of each one's intercrop yield divided by its sole-crop yield; above one means the mixture beats separate fields of the same total area.DEFINED IN Agroforestry overyielding
Land suitability: An agronomic score for how well a crop grows on given soil and climate, independent of who lives there.DEFINED IN New crops and population growth
Land use change: Emissions released when land is converted for agriculture, such as clearing forest or draining peat.DEFINED IN Food miles
Landauer's principle: Erasing one bit at temperature T must dissipate at least kT ln 2 of heat.DEFINED IN Maxwell's demon
Landfill gas: The mixture generated in a buried waste mass, broadly half methane and half carbon dioxide by volume.DEFINED IN Landfill methane
Landmark, route and survey knowledge: Recognising places, knowing procedures between them, knowing relative positions.DEFINED IN Wayfinding
Language bioprogram hypothesis: Bickerton's proposal that children supply innate grammatical defaults where input is impoverished.DEFINED IN Creole genesis
Language shift: A community's movement from habitual use of one language to another across generations.DEFINED IN Heritage language loss
Lapse-rate feedback: The effect of warming being distributed unevenly with height; positive in the stably stratified Arctic, negative in the convecting tropics.DEFINED IN Polar amplification
Last-period problem: The weakening of reputational discipline when a party expects no future dealings.DEFINED IN Brand advertising
Last-term problem: The loss of electoral discipline over an officeholder who cannot stand for re-election.DEFINED IN Term limits
Last-writer-wins: A conflict rule that keeps the change with the highest timestamp and discards the other.DEFINED IN Two systems, one record
Latent demand: Journeys people would make but suppress because the current cost is too high.DEFINED IN Induced traffic
Latent heat: Energy absorbed in evaporation and released on condensation, with no temperature change at the moment of transfer.DEFINED IN Cooling with altitude · Monsoon · Rain shadow
Latent heat of fusion: The energy released when liquid water freezes, about 334 kilojoules per kilogram.DEFINED IN Radiation frost
Latent heat of vaporisation: The energy needed to turn liquid water into vapour with no change in temperature, roughly 2,400 joules per gram here.DEFINED IN Dishwasher drying · Evaporative drying · Heat acclimatization · Heat pipes · Hurricane intensification · Rolling boil versus simmer
Latent heat of vaporization: The energy a liquid absorbs to become vapor at constantDEFINED IN How does a refrigerator cool food?
Latent image speck: The cluster of silver atoms on a grain that, once stable, makes the whole grain developable.DEFINED IN Reciprocity failure
Lateral inhibition: A cell adopting a fate while preventing its immediate neighbours from adopting the same one.DEFINED IN Lateral inhibition in tissue
Lateral movement: Using access to one resource to obtain access to another, typically via credentials found there.DEFINED IN Blast radius
Latewood: The dense dark wood formed late in a growing season.DEFINED IN Tree-ring evidence
Latreia: Worship owed to God alone, in the Byzantine distinction.DEFINED IN Prohibition of images
Law of large numbers: The result that an average over many independent draws converges on its expected value, which is what makes an insurer's total claims predictable.DEFINED IN Insurance · Unstable averages
Law of the minimum: Liebig's principle that yield is governed by the scarcest required resource, not by the total supplied.DEFINED IN Diminishing fertiliser returns
Layer: A tar archive of the filesystem changes made by one build instruction, identified by the hash of its contents.DEFINED IN Layers are diffs
Le Chatelier's principle: The mnemonic that a system at equilibrium shifts to oppose an imposed change; useful, but with known counterexamples.DEFINED IN Ammonia synthesis
Leaching: The extraction by a solvent of unbound, low-molecular-weight material from inside an otherwise intact paint film.DEFINED IN Varnish removal
Leaching fraction: The share of applied water sent past the root zone deliberately, to carry accumulated salt away.DEFINED IN Salinization
Lead time: Elapsed time from a request being made to the work being delivered, including all waiting.DEFINED IN Where the time actually goes
Lead-time bias: The arithmetic lengthening of survival caused by moving the diagnosis date earlier without changing the date of death.DEFINED IN Overdiagnosis
Leading and trailing edge: Dimmers blocking the start of each half-cycle versus its end; the latter suits capacitive electronic loads.DEFINED IN LED dimmer incompatibility
Leading digit: The first non-zero digit of a number, independent of its magnitude or decimal point.DEFINED IN Benford's law
Learning rate: That percentage; an "80 per cent curve" means cost falls to 80 per cent of its previous level per doubling.DEFINED IN Experience-curve pricing · How does a neural network learn?
Lease: A time-bounded grant of a role or resource that must be renewed, so silence causes it to lapse.DEFINED IN Dead or just slow? · Service discovery · Split-brain
Least privilege: Granting only the permissions the task needs, which shrinks the first hop but not the closure.DEFINED IN Blast radius · Prompt injection
Leeway: The small sideways slip of the hull, which sets the keel at its working angle.DEFINED IN Sailing upwind
Left-digit effect: The tendency for a number's perceived magnitude to be fixed disproportionately by its leading digit.DEFINED IN Charm pricing
Legacy nitrogen: Nutrient already applied and stored in soils and groundwater, still en route to the coast years or decades later.DEFINED IN Coastal dead zones
Legal fiction: A classification the law adopts knowing it does not match the ordinary facts, in order to reach a determinate result.DEFINED IN Ritual legal fictions
Legal hold: An instruction that suspends normal disposal for records relevant to anticipated or ongoing litigation.DEFINED IN Data you keep is data you can lose
Legibility: The degree to which a population's wealth and activity can be counted and assessed from outside.DEFINED IN Grain and taxation · Origin of the state
Legislative veto: A mechanism allowing a legislature to cancel executive action without passing a new law, held unconstitutional in the United States in 1983.DEFINED IN Emergency powers ratchet
Legitimacy: The acceptance, at home and locally, that makes a side's continued effort sustainable.DEFINED IN Asymmetric warfare · Everyday legal compliance
Legitimate peripheral participation: Lave and Wenger's term for newcomers doing real but low-stakes work at the edge of a practice, as the means by which they learn it.DEFINED IN Learning a trade by standing there
Lempel-Ziv: A family of methods replacing repeated substrings with references to earlier occurrences.DEFINED IN Lossless compression
Lender of last resort: A central bank lending against sound collateral at a penalty rate to a bank judged illiquid rather than insolvent.DEFINED IN Bank runs
Length bias: The tendency of periodic screening to preferentially detect slow-growing disease, which has a longer detectable phase.DEFINED IN Overdiagnosis
Length constant: The distance over which a gradient falls by a factor of e, set by diffusion balanced against decay.DEFINED IN Morphogen gradients
Lethal trifecta: The combination of private data access, untrusted content, and an outbound communication channel in a single agent context.DEFINED IN Prompt injection
Levee en masse: Inhabitants of unoccupied territory who spontaneously take up arms as an invader approaches.DEFINED IN Combatant identification
Levelling: The progressive loss of detail, qualification and specificity across retellings, paired with sharpening, the growing prominence of the few details that survive it.DEFINED IN Rumour sharpening
Levirate: The practice by which a widow marries her late husband's brother.DEFINED IN Merged kinship terms
Lexical coverage: The proportion of running words in a text that a reader already knows, the variable behind the comprehension threshold.DEFINED IN Vocabulary gap widening
Lexical retrieval: Scoring by matching query terms against an inverted index, weighted by term frequency and rarity; BM25 is the standard scoring function.DEFINED IN Hybrid search
Lexifier: The language supplying most of the vocabulary, typically that of the dominant group.DEFINED IN Creole genesis
Libration: The Moon's small rocking, which lets us see slightly more than half its surface.DEFINED IN Tidal locking
Life expectancy at birth: An average across all deaths including infants, and therefore not the age a typical adult reached.DEFINED IN Post-reproductive life
Life-cycle assessment (LCA): An accounting of a product's environmental burdens across its whole chain, from inputs and land through production, transport, use and disposal.DEFINED IN Food miles
Light interception: The fraction of incoming sunlight caught by the canopy; growth rate rises with it until it saturates near 95 percent.DEFINED IN Grazing rest period
Light limitation: The condition, common in productive grasslands, in which access to light rather than water or nutrients determines which plants persist.DEFINED IN Grazing and grassland richness
Light reactions: The light-driven steps in the chloroplast membranes that split water, release O2, and charge the energy carriers.DEFINED IN Photosynthesis
Lignocellulose: The structural carbohydrate and lignin complex of straw and wood, which mushroom fungi digest and most moulds cannot.DEFINED IN Pasteurised mushroom substrate
Likelihood ratio: How much more probable the evidence is when the belief is true than when false; the multiplier the evidence supplies.DEFINED IN Bayesian updating · Monty Hall problem · Strategic deception
Liminality: Turner's term for the middle phase of a rite of passage, in which the person holds no ordinary social position.DEFINED IN Liminality in initiation
Limit of detection: The concentration high enough to exceed it reliably.DEFINED IN Detection limits
Limitation period: The interval after which a claim or prosecution can no longer be brought.DEFINED IN Statutes of limitation
Linamarase: The cassava enzyme that removes the sugar from linamarin, stored apart from it until the tissue is damaged.DEFINED IN Cassava processing
Lindeberg condition: The technical requirement that no single term dominates, replacing identical distribution.DEFINED IN Ubiquity of the bell curve
Line of communication: The route along which an army is supplied and reinforced from its base.DEFINED IN Military logistics
Lineage: The recorded graph of which datasets are derived from which, and by what transformation.DEFINED IN Lineage
Linear energy transfer: Energy a passing ion deposits per unit path length per unit material density, the axis against which upset rates are measured.DEFINED IN Radiation-hardened spacecraft computers
Linear extension: A total order consistent with every relation in a partial order; a topological sort produces one.DEFINED IN Order from pairwise rules
Linearizability: The strict consistency the theorem uses: every operation appears to take effect at a single instant between its start and its return.DEFINED IN The CAP theorem
Link: A table recording a relationship between hubs, always modelled as many-to-many.DEFINED IN Built never to be rebuilt
Linkage attack: Joining a de-identified release to an identified dataset on shared quasi-identifiers.DEFINED IN Re-identification of anonymized data
Liskov substitution principle: The requirement that an instance of a subtype be usable anywhere the supertype is expected, without weakening what callers may rely on.DEFINED IN Composition over inheritance
Lithium plating: Metallic lithium deposited on the anode when charging is too fast or too coldDEFINED IN Battery ageing
Little's Law: The average number of items in a stable system equals arrival rate times average time in the system.DEFINED IN Backpressure · Batching and the throughput trade · Connection exhaustion before CPU · Limiting work in progress · Where the time actually goes
Live high, train low: Residing at altitude for the hypoxic stimulus while descending for high-intensity sessions.DEFINED IN Altitude training
Load compensation: Varying output with the size of the temperature error, as a modulating boiler does.DEFINED IN Thermostat overshoot
Load control: Deliberately suspending or refusing processes to keep total demand within physical memory.DEFINED IN Memory thrashing
Load factor: The fraction of the bit array set; the analysis' optimum is one half.DEFINED IN Bloom filters · Finding without searching · Hash table clustering
Load shedding: Deliberately refusing work at admission when the signal cannot reach a producer that is able to slow down.DEFINED IN Backpressure · Connection exhaustion before CPU · Rate limiting
Load skew: The difference between the distribution of stored data and the distribution of requests against it.DEFINED IN Hot partitions
Loaded voltage: The terminal voltage measured while current is being drawn, which is what anDEFINED IN Night-time alarm chirp
Loading: The amount by which a premium exceeds the expected claim, covering the insurer's costs, capital and profit.DEFINED IN Insurance
Local estimate: A result that holds for cases near the cutoff, without licensing extrapolation to the whole range.DEFINED IN Class-size cutoff rules
Local mate competition: The situation where offspring of the same mother compete among themselves for mates, which favours a female-biased ratio.DEFINED IN Balanced sex ratios
Local rationality: The principle that people's actions were sensible given their goals, attention, and the information available to them at that moment.DEFINED IN Blameless review
Locality of reference: The empirical tendency of programs to reuse recent data (temporal) and nearby data (spatial).DEFINED IN Caching
Lock-in: The condition of a buyer for whom leaving costs more than staying, arising after purchase rather than before.DEFINED IN Aftermarket pricing · Building sway · Industrial district persistence · Vortex shedding
Lodgement: The area held ashore, deep enough to be defensible and to accommodate the build-up.DEFINED IN Amphibious buildup
Log compaction: Retaining only the most recent record per key, preserving current state while discarding history.DEFINED IN Delivered versus retained · Keeping the history and the snapshot in one file
Log position: A monotonic marker such as a log sequence number, used to resume reading exactly where a consumer left off.DEFINED IN Change data capture
log2(n!): The number of bits needed to name one arrangement of n items; about n log2 n minus 1.44n.DEFINED IN The sorting floor
Logarithmic cost: Cost proportional to the number of times the input can be halved, so doubling the input adds a constant.DEFINED IN Halving the haystack
Logical date: The period a run is for, supplied by the orchestrator, as distinct from the wall-clock time it executes.DEFINED IN Backfilling a pipeline
Logical irreversibility: An operation whose output does not determine its input, such as erasure; the class that carries a thermodynamic cost.DEFINED IN Maxwell's demon
Logical model: Attributes, identifiers, cardinality and normalisation, expressed independently of any database product.DEFINED IN Drawing the same model three times
Logical outgrowth: The requirement that a final rule be a foreseeable development of what was proposed, not something the public never had a chance to address.DEFINED IN Notice-and-comment rulemaking
Logit: The raw score a model assigns to each candidate next token, before it is turned into a probability.DEFINED IN Temperature
Logits: The raw pre-normalisation scores a classifier produces, the most information-rich output an interface can return.DEFINED IN Copying something you can only question
Lognormal distribution: The distribution of a quantity whose logarithm is normal, arising from multiplied contributions.DEFINED IN Ubiquity of the bell curve
Long lot: A narrow strip running back from a river or road, allotted so that every holding shares the frontage.DEFINED IN Cadastral survey patterns
Long tail: The many rare session configurations that collectively account for a substantial share of users but individually appear in no test plan.DEFINED IN Synthetic versus real users
Long-term care: Sustained help with daily living, whether provided by family or paid services, as distinct from medical treatment.DEFINED IN Caregiving load
Longest-prefix match: The rule of choosing the most specific address block containing a destination.DEFINED IN Internet packet routing · Words stored by their beginnings
Longshore drift: The net along-coast movement of sediment produced by waves arriving obliquely to the shore.DEFINED IN Downdrift beach loss · Silted harbours
Loop case: A trolley variant in which the diverted trolley is stopped only by the single victim's body, so his death is needed for the rescue.DEFINED IN Doing versus allowing
LoRA: Low-rank adaptation, training a small added matrix while the base weights stay frozen.DEFINED IN Fine-tuning versus retrieval
Loss aversion: The finding that a loss of a given magnitude is felt more strongly than an equivalent gain.DEFINED IN Clutter · Framing · Sunk cost
Loss factor: How much field energy a material converts to heat at a given frequency.DEFINED IN Selective heating
Loss function: A numerical measure of prediction error.DEFINED IN How does a neural network learn? · Paper folding limit · Rules of thumb on site
Lossless: A coding scheme whose output can be decoded back to the exact original bits.DEFINED IN Lossless compression
Lost in the middle: The observed U-shaped dependence of accuracy on where the relevant information sits in a long input.DEFINED IN Lost in the middle
Lost sales: Purchases that did not occur because the item was unavailable, and which are absent from every transaction record.DEFINED IN Stockout demand censoring
Low energy availability: Insufficient intake relative to training expenditure, a common and separately treatable cause of the same signs.DEFINED IN Overtraining
Low-visibility decision: A decision, typically not to act, that leaves no record and is effectively unreviewable.DEFINED IN Enforcement discretion
Lowest common denominator: The reduced capability set an abstraction can offer, being only what all candidate suppliers support.DEFINED IN The price of being able to leave
LUFS / LKFS: Units of the BS.1770 loudness measure, referenced to full scale.DEFINED IN Broadcast loudness
Lunisolar calendar: One that keeps lunar months but adds whole months to stay with the seasons.DEFINED IN Calendar drift
Lux-hours: Illuminance multiplied by exposure time; the dose photochemical damage is assumed to depend on.DEFINED IN Museum lighting

M

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M/M/c: The standard model of one queue feeding c servers, with random arrivals and random service times; the pooled arrangement.DEFINED IN Single-queue service
MAC: Minimum alveolar concentration: the inhaled agent concentration at which half of patients do not move to a standard surgical incision.DEFINED IN General anaesthesia
MAC-awake: The lower concentration at which half of patients stop responding to a spoken command.DEFINED IN General anaesthesia
Machine unlearning: Research techniques aiming to remove the influence of specific training data from an already-trained model.DEFINED IN Poisoning the well
Macrostate: The coarse description we can actually observe, such as a temperature or a rough left-right split.DEFINED IN Irreversibility
Mafisa: The Tswana term for cattle placed with another household, which keeps the milk and use of the beast.DEFINED IN Herd dispersal among kin
Magic constant: An unexplained literal value, often an anchor to a fact recorded outside the system.DEFINED IN Recovering what the business meant
Magisterium: In Catholic doctrine, the teaching authority charged with authentically interpreting scripture and tradition.DEFINED IN Living interpretation of a fixed text
Magnetic reconnection: The splicing together of oppositely directed magnetic field lines, converting stored magnetic energy into particle motion and heat.DEFINED IN Aurora
Magnetoreception: The ability to sense the Earth's magnetic field for direction.DEFINED IN How do birds know where to migrate?
Magnetotail: The stretched extension of the Earth's field downwind of the Sun, where solar wind energy is stored.DEFINED IN Aurora
Magnitude and intensity: One number for the size of the source, versus a description of the shaking felt at a particular place.DEFINED IN Why do earthquakes happen?
Maillard reaction: The browning cascade between an amino acid and a reducing sugar, named for Louis-Camille Maillard.DEFINED IN Maillard browning
Maimonides' ladder: An eight-level ranking of charity, with mutual anonymity high and enabling self-sufficiency highest.DEFINED IN Anonymous giving
Maimonides' rule: The maximum-of-forty class-formation rule used in Israeli schools, named for its twelfth-century source.DEFINED IN Class-size cutoff rules
Maintenance metabolism: The energy an animal spends merely staying alive, which is the largest single sink in the conversion.DEFINED IN Trophic cost of meat
Maintenance-induced failure: A failure whose cause was introduced by the maintenance work rather than by use.DEFINED IN Failure after repair
Majority-label bias: The pull toward whichever answer label appeared most often among the supplied examples, regardless of the question.DEFINED IN Prompt sensitivity
Maleficium: Harm caused by magical means, the substantive crime charged in most witchcraft trials.DEFINED IN Witch-hunt cascades
Malthusian ceiling: The population a given technology and land base sustains at subsistence, toward which a population-responsive economy tends.DEFINED IN New crops and population growth
Man-in-the-middle: An interceptor who substitutes their own public key, so both ends encrypt correctly to the wrong recipient.DEFINED IN How encryption keeps messages secret
Mandatory minimum: A statutory floor on the sentence for a charge, which transfers sentencing leverage from the judge to whoever selects the charge.DEFINED IN Plea bargaining
Manifest: The document listing an image's layers and configuration.DEFINED IN Tags versus digests · The small files problem
Mantissa: The fractional part of a number's base-10 logarithm; Benford's law is the claim that it is roughly uniform.DEFINED IN Benford's law
Mantissa and exponent: The two fields of a floating-point number, setting resolution within a magnitude and the span of magnitudes reachable.DEFINED IN Model quantization
Mapping: The element-by-element correspondence itself, which carries inferences and not just vocabulary.DEFINED IN Metaphor
MAR: Missingness explained by the observed variables, conditional on which it is unrelated to the missing value.DEFINED IN Dropping incomplete records
Marangoni convection: Flow driven by gradients in surface tension along a free surface, rather than by buoyancy in the bulk.DEFINED IN Convection cells
Marangoni flow: Bulk liquid motion driven by a gradient in surface tension along the surface, whether that gradient comes from composition or from temperature.DEFINED IN Tears of wine
Margin of error: A stated interval around an estimate, conventionally 1.96 standard errors for 95% confidence.DEFINED IN Sample size versus population
Marginal cost: What the next unit costs, as distinct from the average of all; the quantity a fertility decision turns on.DEFINED IN Grandmother proximity and fertility
Marginal customer: The buyer sitting exactly at the boundary between two sellers, whose allegiance a small move can flip.DEFINED IN Retail clustering
Marginal return: The benefit produced by the next unit of investment, as distinct from the total benefit already obtained.DEFINED IN Societal collapse
Marginal utility: The additional satisfaction from one more unit of a good, which falls as you already have more of it.DEFINED IN Paradox of value
Marginalising over reasoning paths: Summing the probability of an answer across all the routes that reach it, instead of taking the single most probable route.DEFINED IN Self-consistency
Marked and unmarked: An option is marked when choosing it says something, which happens only once a default exists to depart from.DEFINED IN Text message tone
Market power: The ability of a seller or buyer to influence price rather than take it as given.DEFINED IN Price signals
Market week: The cycle length on which markets recur, from three or four days to ten, independent of the seven-day calendar.DEFINED IN Market day rotation
Marketing standard: A public specification of size, shape and appearance classes; withdrawn in the EU for most produce types in 2009 in favour of private buyer specs.DEFINED IN Cosmetic produce standards
Martensite: The hard, strained phase formed when steel is cooled too quickly for its dissolved carbon to move out of the lattice.DEFINED IN Alloy strength · Shape-memory alloys
Mass defect: The amount by which a bound nucleus is lighter than the sum of its free constituents.DEFINED IN Nuclear binding energy
Mass elevation effect: The raising of altitudinal limits in the interior of a large mountain mass relative to its outer flanks or to isolated peaks.DEFINED IN Mass elevation effect
Mass ratio: Ignition mass divided by burnout mass, the quantity inside the logarithm.DEFINED IN Rocket staging
Mast cell: A tissue-resident cell holding preformed histamine, which degranulates when surface IgE is cross-linked.DEFINED IN Allergy
Mast seeding: Synchronised, highly variable seed production across a population of plants, at irregular rather than fixed intervals.DEFINED IN Mast seeding
Master wafer: An extra pin in a chamber, creating a second gap so two key depths both clear the shear line.DEFINED IN Master keying
Matched guise: A design in which one speaker records the same passage in two varieties, so evaluations cannot be attributed to voice, content or intelligibility.DEFINED IN Accent and perceived competence
Matching: A statistical method comparing protected sites with unprotected sites of similar terrain and access, to strip out the effect of where parks were placed.DEFINED IN Where parks end up
Matching function: The relationship treating hires as the output of a process whose inputs are unemployed workers and open vacancies.DEFINED IN Vacancies alongside unemployment
Materialised path: Storing each node's full ancestry as a delimited string, so subtrees are prefix matches.DEFINED IN A tree in a table of rows
Materialized view: A stored, engine-maintained result of a query, refreshed on a defined schedule or event.DEFINED IN Denormalization
Matrilateral bias: The observed tendency for contact and support to flow more strongly through the mother's line than the father's.DEFINED IN Grandparent asymmetry
Matrilocal and patrilocal residence: The custom of a couple living near the wife's kin, or near the husband's kin, which strongly shapes which grandparents have access.DEFINED IN Grandparent asymmetry
Matroid: An independence system closed under subsets and satisfying the exchange axiom, for which greed is optimal under every weighting.DEFINED IN When the best step now is safe
Matthew effect: Stanovich's name for cumulative advantage in reading, where existing skill accelerates the acquisition of more.DEFINED IN Vocabulary gap widening
Mature-green harvest: Picking before colour develops, so the fruit can be shipped firm and ripened later with ethylene.DEFINED IN Supermarket tomato flavour
Maturity transformation: Funding long-dated assets with short-dated liabilities, the core service a bank provides.DEFINED IN Bank runs
max_connections: The database's global ceiling, bounded by per-connection memory and process cost.DEFINED IN Connection exhaustion before CPU
Maximum monthly mean (MMM): The long-term average temperature of a reef's warmest month, the local baseline against which stress is measured.DEFINED IN Coral bleaching
MCAR: Missingness unrelated to any data, observed or not; the only mechanism under which deletion is unbiased.DEFINED IN Dropping incomplete records
Mean free path: The average distance a photon travels before being absorbed or scattered.DEFINED IN Photon escape time
Mean lifetime (τ): The average survival time, 1/λ, about 1.44 half-lives.DEFINED IN Radioactive half-life
Mean motion: Revolutions per day, the element in a two-line set that rises visibly as an object decays.DEFINED IN Orbital drag speed-up
Mean radiant temperature: The view-weighted average temperature of the surfaces enclosing a space.DEFINED IN Radiant chill indoors
Mean solar time: Solar time averaged over the year, smoothing out the equation of time.DEFINED IN Time zones
Mean time to recover (MTTR): The arithmetic average of incident recovery durations over a period.DEFINED IN Why the average recovery time lies
Mean-motion resonance: A configuration in which two bodies' orbital periods form a simple whole-number ratio, so their mutual perturbations repeat in phase.DEFINED IN Kirkwood gaps
Measurement uncertainty: The spread of values a procedure could legitimately return for the same event, here dominated by frame timing and body-part choice rather than camera quality.DEFINED IN Video review boundaries
Mechanical advantage: Output force divided by input force; ideally the same as input distance divided by output distance.DEFINED IN Mechanical advantage
Mechanism design: Constructing rules so self-interested play produces the desired outcome.DEFINED IN Envy-free division
Mechanostat: Frost's model of strain thresholds above which bone is added and below which it is removed.DEFINED IN Bone remodelling
Mechanotransduction: The conversion of a mechanical signal into a cellular chemical response.DEFINED IN Tendon rehabilitation loading
Medallion architecture: A naming convention popularised by Databricks for a bronze (raw), silver (cleaned and conformed) and gold (presentation) layering of a data platform.DEFINED IN Refinement stages
Mediator: A variable on the causal path from treatment to outcome; conditioning on it hides part of the effect.DEFINED IN Simpson's paradox · The middleman that reduces connections
Medium of exchange: A good accepted in trade not for its own sake but for onward use.DEFINED IN Origin of money
Meissner effect: The active expulsion of magnetic flux from a superconductor below its transition temperature.DEFINED IN Superconducting levitation
Melanoidins: The large brown polymers that give browned food its colour.DEFINED IN Maillard browning
Melmastia: The obligation of hospitality within Pashtunwali, owed even to an enemy who seeks it.DEFINED IN Guest-right
Melodic contour: The up-and-down shape of a tune, independent of its exact intervals.DEFINED IN Earworms
Memory bandwidth bound: A computation whose speed is limited by moving data to the processor rather than by the arithmetic itself; the normal condition during token generation.DEFINED IN Batching and the throughput trade
Memory cells: Long-lived immune cells that remember a past exposure.DEFINED IN How vaccines work
Memory leak: Memory a program allocates and never releases, so its footprint only grows.DEFINED IN Software aging
Memory poisoning: Planting a durable instruction or false fact via ingested content, to be recalled later as trusted.DEFINED IN What an assistant should forget
Memory-bandwidth bound: Limited by the rate data can be fetched from memory rather than by arithmetic throughput.DEFINED IN Speculative decoding
Memory-bandwidth-bound: Limited by data movement from memory to the processor, not by arithmetic speed.DEFINED IN Prefill and decode
Memory-hard function: One requiring substantial memory per evaluation, limiting how many copies run in parallel on specialised hardware.DEFINED IN Deliberately slow password checks
memory.max / memory.high: Cgroup v2 controls for, respectively, the hard ceiling that triggers the out-of-memory killer and the softer threshold that triggers aggressive reclaim.DEFINED IN Killed with memory to spare
Memorylessness: That a survivor's prospects do not depend on how long it has lasted; the reason the curve is exponential.DEFINED IN Radioactive half-life
Meniscus mirror: A thin, uniformly curved shell blank, stiff enough to handle but not to hold figure unaided.DEFINED IN Large mirror flexure
Mental account: An informal category the mind assigns money to, defined by source, location, or intended use.DEFINED IN Mental accounting
Mental load: The ongoing cognitive work of tracking what a household needs, distinct from performing the tasks.DEFINED IN Proxy arguments
Mental model: The internal account a user forms of how a system works, built largely from the evidence the design provides.DEFINED IN Least astonishment
Menu engineering: Designing a menu's contents, prices and layout to steer choice toward high-margin items.DEFINED IN The dish nobody orders
Mere exposure effect: The tendency to evaluate something more favourably simply for having encountered it repeatedly.DEFINED IN Uninformative advertising · Voice recording mismatch
Merge base: The most recent version common to both lines of work; the third document a three-way merge compares against.DEFINED IN Merge conflicts
Merit system: Appointment and promotion by competitive assessment rather than political patronage.DEFINED IN Civil service tenure
Mersenne Twister: A widely used statistical generator with period 2^19937 - 1, whose state can be recovered from 624 consecutive outputs.DEFINED IN Pseudorandomness
Mesophilic: Describing organisms favouring moderate temperatures; they start a heap and recolonise it during curing.DEFINED IN Compost heat
Meta-analysis: A pooled statistical summary across many studies, used here to show a near-zero average effect.DEFINED IN Choice overload
Metacercaria: The encysted stage that waits in the second host until eaten by the final host.DEFINED IN Parasite host manipulation
Metamer: One of two different spectra that produce identical cone signals and so look identical to a given observer under a given light.DEFINED IN Color mixing
Metastable: Persistently existing in a form that is not the lowest-energy one, because the route to the stable form is blocked by a large barrier.DEFINED IN Carbon allotropes · Supercooling
Metastable failure: A self-sustaining degraded state that persists after its trigger is removed, because the failure itself generates the load that causes it.DEFINED IN Retry storms · The noisy neighbour
Metastable form: A form at rest but not at the lowest available free energy, persisting only because the route to the stable form is blocked.DEFINED IN Disappearing polymorphs
Meteoroid / meteor / meteorite: The object in space, the streak of light, and the surviving fragment on the ground.DEFINED IN Meteor streaks
Metered billing: Charging by counted units of usage rather than by rented capacity.DEFINED IN Metered cost
Metes and bounds: Boundary description by direction, distance and reference to existing features and neighbours.DEFINED IN Cadastral survey patterns
Methanogen: An archaeon that makes methane, from hydrogen and carbon dioxide or from acetate, and only in the absence of oxygen.DEFINED IN Landfill methane
Method versus instrument limit: The difference recovery and matrix effects make.DEFINED IN Detection limits
Methodical battle: The French interwar model of tightly controlled engagements with tempo set by centrally planned artillery.DEFINED IN Doctrine lag
Metonic cycle: The near-coincidence of 19 solar years with 235 lunar months.DEFINED IN Calendar drift
Metre: A repeating template of line length and rhythm that every line in a tradition must satisfy.DEFINED IN Metrical verse
Metres of water equivalent: Overburden as the depth of water supplying the same mass per unit area, so rock and ice compare.DEFINED IN Neutrino detection
Metric definition: The full specification of a measure: its aggregation, its grain, its filters, its time basis and its currency handling.DEFINED IN The semantic layer
Miasma theory: The pre-germ belief that disease arose from foul air, which nonetheless motivated effective sanitation.DEFINED IN Urban mortality
Microbial load: The number of viable organisms present, which together with growth rate sets how long spoilage takes.DEFINED IN Milk spoilage after opening
Microchimerism: The long-term persistence of cells from one individual in another, as fetal cells persist in the mother.DEFINED IN Pregnancy immune tolerance
Microencapsulation: Storing a reactive liquid inside a shell so that it is chemically able to react but physically unable to.DEFINED IN Self-healing coatings
Microstate: A complete specification of every particle's condition; the finest description in play.DEFINED IN Irreversibility
Microtiming: Small departures of note onsets from the metrical grid, measured in milliseconds.DEFINED IN Groove and microtiming
MicroVM: A minimal virtual machine, such as Firecracker, isolating tenants at lower boot cost than a full VM.DEFINED IN Cold starts · Isolates, containers, and startup cost
Mid-Pleistocene transition: The unexplained shift, around one million years ago, from 41,000-year to roughly 100,000-year glacial cycles.DEFINED IN Ice age triggers
Middle lamella: The lignin-rich layer bonding adjacent wood cells sideways; the weak surface along which wood splits.DEFINED IN Screws in end grain
Midpoint overflow: The classic defect where adding two large indices exceeds the integer range; fixed by adding half the difference to the lower index.DEFINED IN Halving the haystack
Mie scattering: Scattering by particles at or above the wavelength's size, affecting all visible colours nearly equally, so looking white.DEFINED IN Why is the sky blue?
Migration: Converting content into a current format, potentially losing some properties.DEFINED IN Digital preservation churn
Milankovitch theory: The account tying glacial cycles to summer insolation at high northern latitudes.DEFINED IN Ice age triggers
Militant democracy: The principle that a democratic order may restrict anti-democratic actors to preserve itself; the term is Karl Loewenstein's, from the 1930s.DEFINED IN Paradox of tolerance
Military revolution: Geoffrey Parker's contested thesis linking these changes to the growth of early modern states.DEFINED IN Obsolete fortifications
Milk fat globule membrane: The phospholipid and protein layer around each fat droplet in milk, which churning strips away.DEFINED IN Butter from cream
Miller-Rabin test: The strengthened test that also checks for a square root of 1 other than plus or minus 1.DEFINED IN Compositeness without factors
Mine hunting: Locating and identifying individual objects on the bottom, as against sweeping, which tries to trigger or cut mines en masse.DEFINED IN Mine warfare
Mineral-associated organic matter: Organic fragments bonded onto clay and silt surfaces, a slow-turnover pool distinct from particulate residue.DEFINED IN Soil carbon loss under ploughing
Mini-dimension: A small separate dimension enumerating the combinations of volatile, low-cardinality attributes, keyed directly from the fact table.DEFINED IN Rapidly changing attributes
Minimal disruption: The property that a membership change relocates only about one key in n.DEFINED IN Adding a machine without moving the data
Minimal pair: Two words differing in exactly one contrastive unit, the standard proof that the unit is real.DEFINED IN Sign language
Minimax or Nash equilibrium: A pair of strategies from which neither player can profit by unilaterally changing, which in this game requires both to mix.DEFINED IN Penalty aiming
Minimum connecting time: The shortest interval an airport and airline will sell between an arrival and an onward departure.DEFINED IN Missed connections
Minimum efficient scale: The smallest output at which average cost has essentially stopped falling.DEFINED IN Industry concentration
Minimum length of stay (MinLOS): A rule requiring a stay arriving on a given date to run at least so many nights.DEFINED IN Length-of-stay controls
Minimum mass: The lower bound on a planet's mass returned by radial velocity alone, since the orbital tilt is unknown.DEFINED IN Exoplanet detection
Minimum-norm solution: Among all exact fits, the one with the smallest coefficients; what gradient descent from a small start tends to find.DEFINED IN Double descent
Minor histocompatibility antigens: Ordinary self-proteins whose sequence varies between individuals, sufficient to drive rejection even between HLA-identical siblings.DEFINED IN Transplant rejection
Mirror therapy: Treatment using a mirrored image of the intact limb as feedback for the missing one.DEFINED IN Phantom limb pain
Misfit stream: A stream far too small for the valley it occupies, typically because it was beheaded.DEFINED IN River capture
Misinformation effect: The incorporation of post-event information into the memory of the event itself.DEFINED IN Memory reconstruction
Mismatched generalisation: The failure mode where an input falls outside the distribution safety training covered but inside the model's capabilities.DEFINED IN Talked out of its own rules
Misprediction penalty: The cycles lost discarding speculative work and refilling the front end after a wrong guess.DEFINED IN Branch prediction
Missing fundamental: The pitch heard at a harmonic series' spacing when no energy is present at that frequency.DEFINED IN Telephone bandwidth
Missing not at random: Absence from a dataset that is itself informative, rather than an accident of collection.DEFINED IN Survivorship bias
Mit'a: The Inka system of rotational labour service, a tax paid in work rather than produce.DEFINED IN Grain and taxation
Mitscherlich function: The smoothed diminishing-returns curve, Y = A(1 - e^(-cN)), fitted to nutrient response.DEFINED IN Diminishing fertiliser returns
Mixed chimerism: A state in which donor and recipient blood-forming cells coexist, so developing T cells reactive to the donor are deleted rather than merely suppressed.DEFINED IN Transplant rejection
Mixed grain: A table whose rows do not all mean the same thing, which silently corrupts counts and averages.DEFINED IN What one row stands for
Mixed strategy: A way of playing that randomises over several actions in fixed proportions, rather than always choosing one.DEFINED IN Penalty aiming · Randomized screening
Mixture of populations: A group made of subgroups with different failure rates, whose combined rate falls over time even when no subgroup's does.DEFINED IN Bathtub failure curve
MNAR: Missingness that depends on the unobserved value itself; not distinguishable from MAR using the data at hand.DEFINED IN Dropping incomplete records
Mnemonic acronym: A memorable word formed from initial letters, whose value is retrieval rather than content.DEFINED IN Twenty-five acronyms, nine pieces
Mobile phase: The solvent advancing through the paper, carrying whatever is dissolved in it at that instant.DEFINED IN Paper chromatography
Mobility: How readily a carrier drifts under an applied field, reduced by scattering from the very dopants that supplied it.DEFINED IN Semiconductor doping
Mock server: A server generated from a specification that returns valid responses, unblocking client work.DEFINED IN Agreeing the shape before the substance
Modal dispersion: Pulse spreading caused by different guided paths having different lengths, eliminated in single-mode fibre.DEFINED IN Guided light
Modality gap: The observed separation between image and text regions of a jointly trained embedding space.DEFINED IN Multimodal fusion
Mode: The pattern of intervals a melody draws on — major and minor being two of many, and the one most often mistaken for a fixed emotional code.DEFINED IN How can music create emotion?
Model collapse: Progressive degradation of a generative model trained on data produced by earlier generations of models.DEFINED IN Model collapse
Model extraction: Reconstructing a model, or a functional substitute for it, from its responses to chosen queries.DEFINED IN Copying something you can only question
Model turn: One round of generation between two tool calls, and therefore one more opportunity for the sequence to go astray.DEFINED IN Tool granularity
Model-as-judge: Using a language model to score another's output against a rubric; scalable, with biases needing calibration.DEFINED IN Evaluating retrieval separately
Model-graded check: Using a language model to score another model's output; the most flexible tier of checking and the one that most needs auditing.DEFINED IN Evaluation suites
Moderator: A variable that changes the size or direction of an effect, so the effect holds under some conditions and not others.DEFINED IN Choice overload
Modified rejection sampling: The accept-or-resample rule that makes emitted tokens follow the target model's distribution exactly.DEFINED IN Speculative decoding
Modular exponentiation by squaring: Computing a large power modulo n in a number of steps proportional to the exponent's bit length.DEFINED IN Compositeness without factors
Modulational instability: The Benjamin-Feir growth of sidebands in a narrow-banded wave train, concentrating energy into fewer, larger waves.DEFINED IN Rogue waves
Module-level replacement: Servicing by swapping a whole assembly rather than the individual failed component within it.DEFINED IN Repair economics
Module-scope variable: A value whose lifetime is the process, not the request; the commonest accidental home for request-scoped data.DEFINED IN Warm reuse leaks
Modus ponens / modus tollens: The two valid moves on a conditional — from "if P then Q" plus PDEFINED IN What makes an argument logically valid?
Moisture migration: Slow transport of water through a stored bulk by convection driven by a core-to-shell temperature difference.DEFINED IN Grain bin hot spots
Molecular cloud: The cold, dense phase of interstellar gas, around ten kelvin, in which star formation occurs.DEFINED IN Star formation
Molecular mimicry: Resemblance between a pathogen antigen and a self antigen, so an anti-microbial response also attacks host tissue.DEFINED IN Autoimmunity
Moment of inertia: How hard a body is to spin about a given axis: each bit of mass counted with the square of its distance from that axis.DEFINED IN Figure-skating spin
MOND: Modified Newtonian dynamics, a proposal that gravity departs from Newton's law below a very small acceleration.DEFINED IN Galaxy rotation curves
Money illusion: Treating a nominal change as if it were a real one, as when a freeze under inflation is accepted but an equivalent cut is not.DEFINED IN Wage stickiness
Money multiplier: The deposits-to-reserves ratio implied by the re-lending cascade; arithmetically valid, causally misleading.DEFINED IN Bank money creation
Money supply: The total amount of money circulating in an economy.DEFINED IN What is inflation?
Monitoring cost: The measurable slowing of an ongoing task caused by holding and watching for an intention.DEFINED IN Prospective memory
Monoculture: Cultivation of a single crop, and often a single variety, over a large area.DEFINED IN Monoculture fragility
Monomyth: Campbell's proposed universal departure-initiation-return arc underlying world mythology.DEFINED IN Story shape
Monopole: A single radiating element fed against a conducting plane, electrically equivalent to half a dipole.DEFINED IN Antenna ground plane
Monotonic key: A key that only increases, such as a timestamp or sequence number, which concentrates all writes on the newest range partition.DEFINED IN Hot partitions
Monotonic reads: The guarantee that a client never sees a value older than one already seen.DEFINED IN Replication lag
Mood repair: Acting to relieve a present bad feeling, here by turning from the task causing it.DEFINED IN Why do we procrastinate?
Moral cleansing: Affirming or acting on a value after it has been symbolically threatened, to restore standing.DEFINED IN Pricing the sacred
Moral crumple zone: Madeleine Elish's term for a human placed where they will absorb blame for a failure they had little practical capacity to prevent.DEFINED IN Rubber-stamped review
Moral hazard: Hidden action after contracting, so behaviour changes once the risk is borne by someone else.DEFINED IN Adverse selection · Experience rating
Moral understanding: A grasp of why an act has the moral status it has, as distinct from knowing that it does.DEFINED IN Taking moral advice on trust
Moral worth: The value an act has in virtue of the motive it was done from, not merely its rightness.DEFINED IN Taking moral advice on trust
Moran effect: Population-wide synchrony produced by a weather variable shared across a region rather than by interaction between individuals.DEFINED IN Mast seeding
Morphogen: A signalling molecule that acts at a distance in graded fashion, different concentrations producing different outcomes.DEFINED IN Morphogen gradients
Morphophonemic spelling: Spelling that keeps a unit of meaning visually constant even when its pronunciation varies.DEFINED IN Spelling reform
Motivated reasoning: Belief shaped by preference through selective attention rather than by decision.DEFINED IN Believing at will
Motivation crowding out: Displacement of an internal or social motive by an introduced external incentive.DEFINED IN Paying pupils to read · Pricing the sacred
Motor unit: One motor neuron together with all the muscle fibres it commands; it fires all-or-nothing.DEFINED IN Early strength gains
Movable feast: An observance whose date is recomputed each year from an astronomical rule rather than fixed to a calendar day.DEFINED IN Festival calendars
Movement joint: A deliberate full-depth break in a tiled field, filled with a compressible material so it transmits no force across itself.DEFINED IN Movement joints in tiling
Moving block: Signalling that computes safe separation continuously from each train's position and braking curve, rather than by fixed track sections.DEFINED IN Mixed-speed rail capacity
Moving to Opportunity: A randomised US experiment offering housing vouchers to move out of high-poverty areas, the main experimental evidence on neighbourhood effects.DEFINED IN Persistent poor neighbourhoods
Muller's ratchet: The irreversible accumulation of deleterious mutations in a finite population without recombination.DEFINED IN Cost of sexual reproduction
Multi-layer insulation: Stacked reflective sheets separated by vacuum, blocking radiative transfer the way a blanket blocks conduction on Earth.DEFINED IN Spacecraft cooling
Multi-stage build: A build file with several independent stages, where the final stage copies only chosen artifacts from earlier ones.DEFINED IN Building somewhere you do not ship from
Multi-year procurement: A contract committing orders across several budget years, the instrument that makes new capacity financeable.DEFINED IN Munitions stockpiles
Multihoming: Using several competing platforms at once, which weakens both tipping and lock-in.DEFINED IN Network effects
Multilateral reputation mechanism: Enforcement by the collective refusal of a whole group to deal with someone who has cheated any of its members.DEFINED IN Trade diasporas
Multiple imputation: Filling blanks several times from a model and combining the results so imputation uncertainty enters the final interval.DEFINED IN Dropping incomplete records
Multiplication factor (k): The average number of fissions in one generation caused by the previous generation's fissions.DEFINED IN Critical mass
Muscle spindle: A stretch receptor inside the muscle that excites its own motor neurons.DEFINED IN Muscle cramp
Musical expectation: A listener's prediction about what sound will come next.DEFINED IN How can music create emotion?
Mutation accumulation: Medawar's account: late-acting deleterious mutations persist because selection barely removes them.DEFINED IN Senescence
Mutual capacitance: Sensing the coupling between a driven row and a sensed column, giving one independent measurement per crossing.DEFINED IN Capacitive sensing
Mutual exclusivity: The working assumption that a new word refers to something that does not already have a name.DEFINED IN Child word learning
Mutual inhibition: Two neural populations each suppressing the other, so that one being active keeps the other down.DEFINED IN Binocular rivalry
Mutual TLS: Encryption in which both ends present certificates, giving each workload a verified identity.DEFINED IN Moving failure handling out of the program
Mutualism: An association in which both partners net a benefit, whatever mechanism holds it together.DEFINED IN Symbiosis
MVCC: Multi-version concurrency control — keeping several versions of a row so readers see a consistent snapshot without blocking writers.DEFINED IN Database transactions
Mycorrhiza: A fungus-root association that intercepts nutrients from decomposing litter and delivers them to the plant.DEFINED IN Dust-fed rainforests
Myelin: The insulating sheath around large axons that allows impulses to jump between gaps, greatly speeding conduction.DEFINED IN Pins and needles

N

N+1 problem: One query for a list followed by one query per element, produced by naive per-field resolution.DEFINED IN Letting callers ask for exactly what they want
N170: A negative electrical response about 170 ms after a face is seen, larger for faces than other objects and also elicited by illusory faces.DEFINED IN Pareidolia
Namespace: A kernel facility giving a group of processes their own instance of a global resource, such as the process table or the network stack.DEFINED IN Isolation without a machine
Natural bed: The orientation the stone lay in at the quarry, beds horizontal.DEFINED IN Natural bed in stone
Natural decrease: Deaths exceeding births in a population, independent of migration.DEFINED IN Rural depopulation
Natural density: The limiting fraction of the first N integers a set occupies; uniform and finitely additive, but not countably additive.DEFINED IN Fair lottery over the integers
Natural enemies: The predators, parasitoids and pathogens that suppress a herbivore population without intervention.DEFINED IN Pest resurgence
Natural experiment: A real-world change that isolates one variable, as the 2010 swimsuit ban did for equipment.DEFINED IN Falling records · Grandmother proximity and fertility · Home advantage
Natural frequency: The rate at which a structure oscillates on its own after being disturbed, set by its stiffness and mass.DEFINED IN Resonance · Vibration isolator resonance
Natural increase: Births minus deaths, excluding migration.DEFINED IN Urban mortality
Natural or business key: An identifier that already exists in the business, such as a customer code or an ISBN.DEFINED IN Surrogate keys
nDCG: Normalised discounted cumulative gain, a ranking measure that rewards putting relevant items nearer the top.DEFINED IN Evaluating retrieval separately
Near field: The region close to a source where amplitude falls steeply with distance, so a small separation gives a large amplitude difference.DEFINED IN Microphone proximity effect
Near field and far field: The region close to the melting source, where sea level falls, and the distant ocean, where it rises by more than the global mean.DEFINED IN Sea level fingerprints
Near miss: An event in which the causal sequence of an accident occurred but the harmful outcome did not.DEFINED IN Near misses
Near transfer: Applying learning to a situation closely resembling the one it was learned in.DEFINED IN Transfer of learning
Nearest neighbour search: Finding the stored vectors closest to a query vector under some distance measure.DEFINED IN Approximate nearest neighbour search
Nearest-neighbour method: Any procedure that predicts or retrieves by finding the closest recorded examples under a distance.DEFINED IN Curse of dimensionality
Neck cutoff: A flood breaching the narrow land between two limbs of a loop, abandoning it.DEFINED IN River meanders
Necrosis: Uncontrolled death from overwhelming injury, in which the cell swells, ruptures, and spills its contents.DEFINED IN Programmed cell death
Nectar robbing: Taking nectar without contacting the reproductive parts, often through a hole bitten in the side.DEFINED IN Pollination specificity
Nectar spur: A tubular extension holding nectar at its far end, reachable only by a long enough tongue or bill.DEFINED IN Pollination specificity
Needle in a haystack: An evaluation that hides one fact at a chosen depth in a long context and tests whether the model retrieves it.DEFINED IN Lost in the middle
Negative attributes: Maimonides' doctrine that only denials can be truly asserted of God, each one narrowing error.DEFINED IN Speaking of the unspeakable
Negative cycle: A loop of total negative length, around which a path can be shortened indefinitely, so no shortest path exists.DEFINED IN Nearest first · Negative edge weights
Negative differential resistance: A region where voltage across a device falls as current through it rises, so its characteristic slopes downward even though the voltage is positive.DEFINED IN Ballast in a gas discharge
Negative energy balance: The period when energy leaving in milk and maintenance exceeds energy taken in as feed.DEFINED IN Dairy cow energy balance
Negative existential: A sentence denying that something exists, which seems to need the thing in order to deny it.DEFINED IN Talking about what does not exist
Negative face: The wish to act unimpeded by others, which any request necessarily presses on.DEFINED IN Indirect requests
Negative frequency dependence: A payoff that falls as the strategy carrying it becomes more common, producing a stable mixture rather than a winner.DEFINED IN Left-hander advantage
Negative object: An aim achieved by preventing something rather than accomplishing something, which is what defence alone can deliver.DEFINED IN Defender's advantage
Negative reinforcement: Strengthening a behaviour by removing something aversive, as when an escalation gets a demand withdrawn.DEFINED IN Worst behaviour at home
Negative result: A confirmed absence, as distinct from a gap in coverage.DEFINED IN Writing down what you could not determine
Negativity bias: The general tendency for negative events to weigh more heavily than comparable positive ones.DEFINED IN Trust asymmetry
Nematic phase: A liquid-crystal phase with orientational order but no positional order.DEFINED IN Liquid crystals
Neolocal residence: The expectation that a married couple forms a new, separate household rather than joining an existing one.DEFINED IN Late marriage and population restraint
Nested sets: Numbering nodes by traversal with a left and right value, so a subtree is a numeric range.DEFINED IN A tree in a table of rows
Network effect: The increase in a choice's value as more people make the same choice.DEFINED IN Technical standards
Neural adaptation: The decline in a population's response under sustained drive, which here erodes the winner's own suppression.DEFINED IN Binocular rivalry
Neural crest: An embryonic cell population contributing to pigment, facial cartilage and adrenal tissue, proposed as the link behind the syndrome.DEFINED IN Domestication
Neuroma: A tangle of regrowing fibres at a cut nerve end, which can fire spontaneously.DEFINED IN Phantom limb pain
Neuronal recycling: Dehaene's proposal that cultural inventions colonise brain circuits evolved for older purposes.DEFINED IN Reading acquisition
Neutral axis: The surface through the thickness whose length is unchanged by bending; the fibre along which blank length is conserved.DEFINED IN Bend allowance · Reinforced concrete · Suspension bridge cables
Neutral buoyancy: The condition in which displaced weight and own weight are equal, so the object neither rises nor sinks.DEFINED IN Buoyancy
Neutral drift (random copying): A model in which choices are copied in proportion to current frequency with a small innovation rate, reproducing fashion-like turnover with no preference for distinctiveness.DEFINED IN Given-name fashions
Neutral plane: The plane through a panel's thickness about which bending moments are reckoned.DEFINED IN Balanced veneer
Neutrality: Indifference as to which party's aims prevail, which an impartial mission need not have.DEFINED IN Peacekeeping mandates
Neutron leakage: Neutrons escaping through the outer surface before causing a fission; the loss term that makes size matter.DEFINED IN Critical mass
New production: Growth supported by nutrients newly supplied to the lit layer from outside it; the part that can be exported or harvested.DEFINED IN Ocean productivity
News values: The shared criteria by which journalists judge an event worth reporting, such as scale, unexpectedness and proximity.DEFINED IN Media sameness
Nicaraguan Sign Language: The language that emerged among deaf Nicaraguan schoolchildren after 1977 and was regularised by the cohorts that learned it.DEFINED IN Sign language
Niche picking: Selecting an activity partly for its vacancy rather than for one's aptitude at it.DEFINED IN Sibling deidentification
Nitrogen fixation: Conversion of atmospheric nitrogen into biologically usable form by certain microbes.DEFINED IN Soil formation
Nitrogenase: The bacterial enzyme that breaks the N2 bond, the step no plant performs for itself.DEFINED IN Crop rotation · Leghemoglobin in root nodules
No-show: A passenger holding a valid booking who does not present for the flight.DEFINED IN Overbooking
Nocebo effect: Symptoms produced by the expectation of harm rather than by any active cause.DEFINED IN Placebo effect
Nociceptor: A sensory neuron specialised to detect potentially damaging stimuli; its firing is not itself pain.DEFINED IN Central sensitization · Delayed muscle soreness
Nodal precession: The slow rotation of an orbit's plane caused by Earth's equatorial bulge, at a rate depending on altitude and inclination; it is what smears a fragment cloud into a shell.DEFINED IN Orbital debris cascade
Node: Either of the two points where the Moon's orbit crosses the plane of Earth's orbit; eclipses can only happen near one.DEFINED IN Eclipse seasons
Nomina sacra: The contracted forms of divine names in Christian manuscripts, marked as sacred rather than shortened for space.DEFINED IN Scribal abbreviation
Nominal and effective rate: The advertised annual rate, versus what it actually comes to once the compounding periods within the year are counted.DEFINED IN Compound interest
Non-additive measure: A ratio or average, which must be recomputed from components rather than aggregated.DEFINED IN What one row stands for
Non-aeronautical revenue: Income from retail concessions, food and beverage, parking and property.DEFINED IN Airport layout
Non-apology: Words expressing regret while withholding acknowledgement of the act and responsibility for it.DEFINED IN Apology and repair
Non-climacteric fruit: Fruit lacking that surge, which will not sweeten once picked.DEFINED IN Ripening by contagion
Non-constructive proof: An argument establishing that something exists without indicating how to find or build it.DEFINED IN Pigeonhole principle
Non-determinism error: The engine's response when replay requests an operation the history does not match.DEFINED IN Replay determinism
Non-distributive responsibility: Responsibility borne by a group that does not divide into shares carried by its members.DEFINED IN Collective responsibility
Non-excludable: A good from which a non-payer cannot practically be barred.DEFINED IN Compulsory taxation
Non-functional overreaching: The same dip without the rebound, resolving over weeks to months.DEFINED IN Overtraining
Non-functioning distractor: An option almost nobody selects, raising the chance of a lucky guess without adding anything.DEFINED IN Diagnostic distractors
Non-inferiority trial: A trial designed to show that a new approach is not meaningfully worse than the standard, rather than that it is better.DEFINED IN Antibiotic course length
Non-informative censoring: The assumption that those censored at any time have the same future risk as those who remain.DEFINED IN Censored follow-up
Non-manual marker: Grammatical information carried on the face and head, such as brow raise for a yes/no question.DEFINED IN Sign language
Non-random assignment: Systematic allocation of particular pupils to particular teachers, which produces error that repeats rather than averaging out.DEFINED IN Value-added ranking instability
Non-response bias: Error arising when those who answer differ systematically from those who do not; unaffected by sample size.DEFINED IN Sample size versus population
Non-rival: A good whose enjoyment by one person leaves no less for anyone else.DEFINED IN Compulsory taxation
Non-stationary process: One whose statistical behaviour, such as its mean rate, changes over time, so past averages do not predict future values.DEFINED IN Progress-bar estimates
Non-thermal escape: Loss driven by energy from elsewhere: photochemical recombination, ion pickup by the solar wind, and sputtering, as opposed to thermal escape from the tail of the molecular speed distribution.DEFINED IN Martian atmosphere loss
Nonce: A value used once, whose freshness is what makes a captured transcript useless later.DEFINED IN A secret you never send
Nonshared environment: Everything experienced individually rather than in common, plus measurement error; large, and largely unexplained.DEFINED IN Sibling differences
Normalisation: Organising attributes so each fact is recorded in exactly one place, removing update anomalies.DEFINED IN Drawing the same model three times
Normalisation rule: A declared claim that some class of difference is irrelevant to the comparison.DEFINED IN Running both and comparing
Normalization of deviance: The gradual reclassification of an out-of-specification condition as acceptable, after it repeatedly produces no harm.DEFINED IN Near misses
Normalized gain: The fraction of the available improvement a class actually achieved, used to compare courses with different starting points.DEFINED IN Classroom misconceptions
Normative influence: Conforming in order to be accepted, without changing what one believes; undone by private responding.DEFINED IN Conformity
Not-before timestamp: A per-subject cutoff invalidating all tokens issued before a given moment.DEFINED IN You cannot un-issue a signature
Notch: A membrane receptor whose activation by a neighbour's ligand releases an intracellular fragment that travels to the nucleus.DEFINED IN Lateral inhibition in tissue
Notch sensitivity: The extent to which a material's fatigue strength actually falls by the full geometric factor.DEFINED IN Stress concentration
Notice of proposed rulemaking: The published proposal that opens the comment period, which must be specific enough for the eventual rule to count as noticed.DEFINED IN Notice-and-comment rulemaking
Nucleon: A proton or a neutron, the constituents of a nucleus.DEFINED IN Nuclear binding energy
Nucleus sampling (top-p): Drawing the next token from the smallest set of candidates whose probabilities sum to a chosen threshold.DEFINED IN One improbable word · Temperature
Null recurrence: Return is certain, but the expected time until it happens is infinite.DEFINED IN Random walk recurrence
Number needed to treat (NNT): One divided by the ARR, over a stated horizon and comparator.DEFINED IN Number needed to treat
Numerical identity: Being one and the same thing, as opposed to being exactly alike (qualitative identity).DEFINED IN Identity over change
Nutation: The small nodding superimposed on precession, most visible just after a gyroscope is released.DEFINED IN Gyroscopic precession
Nyquist frequency: Half the sampling rate, the upper limit on signal content for unambiguous reconstruction.DEFINED IN Aliasing
Nyquist limit: The highest frequency representable at a given sampling rate, equal to half of it.DEFINED IN Telephone bandwidth

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OAuth 2.0: A delegated authorization framework in which a resource owner grants a client limited access to a resource server without sharing credentials.DEFINED IN Delegation without the password
Obiter dicta: Remarks not necessary to the outcome, persuasive at most.DEFINED IN Legal precedent
Object store: Storage addressed by object name, where a write replaces a whole object and nothing spans two.DEFINED IN Transactions on immutable storage
Objective control: Huntington's bargain trading professional autonomy for political abstention by officers.DEFINED IN Civilian control
Obligate biotroph: An organism that can obtain carbon only from a living host, and so has no independent existence.DEFINED IN Mycorrhizal carbon trade
Obligate symbiosis: A relationship in which one or both partners can no longer survive alone, typically after losing capacities the partner supplies.DEFINED IN Symbiosis
Obligation: An instruction returned alongside a permit that the enforcement point must perform, such as masking a field or writing an audit record.DEFINED IN Deciding apart from enforcing
Obliquity: The tilt of a body's spin axis relative to its orbit, which governs how strongly seasons are expressed.DEFINED IN Pluto's seasonal atmosphere
Observability: The ability to answer new questions about a system's internal state from its existing outputs, without shipping new instrumentation.DEFINED IN Unknown unknowns
Observable universe: The region close enough that light emitted since the beginning has had time to reach us.DEFINED IN Dark night sky
Occluded carbon: Organic matter physically enclosed within aggregates and thereby protected from decomposition.DEFINED IN Soil carbon loss under ploughing
Occluded cell: A small volume of solution whose exchange with the bulk is restricted enough that its chemistry diverges from it.DEFINED IN Crevice corrosion
Occluded phosphorus: Phosphorus adsorbed onto or enclosed within iron and aluminium oxides, chemically present but largely unavailable to plants.DEFINED IN Dust-fed rainforests
Occlusion: The closing off of blood flow, here caused by the contracting muscle's own internal pressure.DEFINED IN Forearm pump in climbing
Occlusion effect: The boost in perceived loudness and depth of one's own voice when the ear canals are blocked.DEFINED IN Voice recording mismatch
Occurrence seriation: Ordering by which types are present or absent, ignoring their proportions.DEFINED IN Ceramic seriation
Octahedrite: An iron meteorite whose kamacite plates grew on the four {111} plane sets of a parent taenite crystal, producing the Widmanstatten figure.DEFINED IN Widmanstatten pattern
Odorant receptor: A protein in the nasal lining that binds a range of airborne molecules and signals when it does.DEFINED IN Smell coding
Off-ramp: An arranged step down that lets a side concede without appearing to have been beaten.DEFINED IN Escalation
Off-record strategy: Saying something whose intended request is inferable but not stated, so the speaker can disclaim it.DEFINED IN Indirect requests
OFF-score: A derived index combining haemoglobin with reticulocyte percentage, designed to expose high oxygen capacity alongside suppressed production.DEFINED IN Athlete biological passport
Offence-defence balance: Whether a given amount of military effort achieves more for the attacker or the defender in a given period and setting.DEFINED IN Security dilemma
Offset: A consumer's recorded position in a partition, owned by the consumer rather than the broker.DEFINED IN Delivered versus retained · Green wave signal timing · Order within a slice
Offset commit: A consumer recording its position, which is how it ends the broker's redelivery obligation.DEFINED IN When responsibility transfers
Offset pagination: Resuming by counting past a number of rows; simple, but wrong when the collection changes mid-traversal.DEFINED IN Opaque cursors
OLAP: Online analytical processing: large aggregate queries over many rows and few columns.DEFINED IN Two stores for one truth
Olbers' paradox: The argument that an infinite, eternal, uniformly starred universe would have a uniformly bright sky.DEFINED IN Dark night sky
Olfactory bulb: The first processing stage for smell, sitting beneath the front of the brain and receiving fibres directly from the nose.DEFINED IN Smell and memory
OLTP: Online transaction processing: many small, correctness-critical operations on few rows each.DEFINED IN Two stores for one truth
Ombak: Literally "wave"; the shimmer produced by sounding two deliberately mistuned paired instruments.DEFINED IN Gamelan tuning
On-farm loss: Crop that never leaves the field, whether ungraded, unharvested or unsold; defined inconsistently across studies, which is why totals disagree.DEFINED IN Cosmetic produce standards
On-time performance: The share of flights arriving within a defined margin of the published schedule, fifteen minutes in United States reporting.DEFINED IN Schedule padding
On/off (bang-bang) control: A controller whose output has only two values, full on and full off.DEFINED IN Thermostat overshoot
One-shot game: An interaction the parties expect never to repeat, so no future consequence disciplines present behaviour.DEFINED IN Landmark restaurants
One-sided error: An error that can occur in only one direction, so one of the two answers is a guarantee.DEFINED IN Bloom filters
One-time code: A short-lived value proving possession of a phone or seed, presentable by anyone who obtains it in time.DEFINED IN Why a code sent to your phone does not stop phishing
Onsight: Climbing a route first try with no prior information, the convention that isolates a route's difficulty from accumulated beta.DEFINED IN Climbing grade drift
oom_score_adj: A per-process bias applied to the out-of-memory killer's victim scoring.DEFINED IN Killed with memory to spare
Opacity limit: The density at which a fragment becomes opaque to its own radiation, trapping heat and halting further fragmentation.DEFINED IN Star formation
Opaque token: A value a client must pass back unmodified and must not parse or construct.DEFINED IN Opaque cursors
Open access: A resource nobody may exclude anyone from, which is the case these commons are usually mistaken for.DEFINED IN Common high pasture
Open addressing: Resolving collisions by probing other slots in the table itself rather than chaining off each slot.DEFINED IN Hash table clustering
Open texture: Hart's term for the irreducible margin of cases a general rule leaves undecided.DEFINED IN Living interpretation of a fixed text
Open-closed principle: The guideline that a module should be extensible without its source being modified.DEFINED IN Wrapping without changing
Open-field system: An arrangement in which a village's arable lies in large unfenced fields divided into strips, farmed under collective rules of rotation and grazing.DEFINED IN Scattered strip farming
Open-label placebo: An inert treatment given with the patient fully informed that it is inert.DEFINED IN Placebo effect
Open-pollinated variety: A variety that reproduces a stable population from its own saved seed rather than a single constructed genotype.DEFINED IN Hybrid seed decline
OpenAPI / AsyncAPI / Protobuf: Specification formats for HTTP APIs, event-driven APIs, and RPC interfaces respectively.DEFINED IN Agreeing the shape before the substance
OpenID Connect: The identity layer over OAuth 2.0 that supplies a verifiable assertion about who the user is.DEFINED IN Delegation without the password · Three questions people treat as one
Operational reserve: The uncommitted formation a defender holds back, whose release timing is what the confusion actually attacks.DEFINED IN Airborne drop dispersion
Operative temperature: The index of air and radiant temperature that predicts comfort; roughly their average.DEFINED IN Radiant chill indoors
Opportunity cost: What must be given up to produce something, measured in the next best use of the same resources.DEFINED IN Comparative advantage · Internal transfer pricing · Where parks end up
Opportunity cost account: The view that effort feels costly because alternatives to it grow more attractive, rather than because a resource is consumed.DEFINED IN Decision fatigue
Opportunity cost of labour: The earnings a worker gives up by staying in one occupation, which is what an employer must actually match.DEFINED IN Cost disease
Opportunity structure: The arrangement of settings that determines who a person can realistically encounter, and therefore choose between.DEFINED IN Similar partners
Optical cavity: The mirror pair feeding light back through the gain medium, selecting the mode that survives a round trip.DEFINED IN Laser coherence
Optical figure: How closely a mirror's surface matches its intended shape, measured against the wavelength of light.DEFINED IN Large mirror flexure
Optical molasses: The viscous force from counter-propagating red-detuned beams, which cools but does not confine.DEFINED IN Laser cooling
Optical size: The intended reading size a particular cut of a typeface was drawn for, now often exposed as an interpolating axis in a variable font.DEFINED IN Optical sizes in type
Optimal substructure: The property that a problem's solution is built from optimal solutions of its subproblems; the second requirement for dynamic programming.DEFINED IN Remembering the sub-answers · When the best step now is safe
Optimistic concurrency: Detecting a conflicting concurrent change at write time, typically via a version number, rather than preventing it with a lock.DEFINED IN Collecting changes before committing them · Merge conflicts · Transactions on immutable storage
Option value: The worth of holding a capacity you will probably not use, arising from uncertainty about who will need it and the cost of getting it late.DEFINED IN Unused curriculum
Oracle: Whatever supplies the correct answer a test compares against; here, the legacy system itself.DEFINED IN Running both and comparing
Oral-formulaic theory: The account of oral epic developed by Milman Parry and Albert Lord from fieldwork with South Slavic singers.DEFINED IN Oral tradition
Orbital resonance: A repeating timing relationship between orbits that lets small nudges accumulate, clearing or confining material.DEFINED IN Planetary rings
Orchestration: Coordination by direction, where one component holds the sequence and invokes each participant in turn.DEFINED IN Choreography versus orchestration · Orchestration
Orchestrator: The component that decomposes a task, dispatches subtasks, and merges what comes back.DEFINED IN Many agents, one task
Ordinal scale: A rank ordering with no unit and no fixed reference, so its meaning depends entirely on the items being ranked.DEFINED IN Climbing grade drift
Origin: The scheme + host + port of a page (e.g. https://mysite.com); "cross-origin" means a different one.DEFINED IN CORS in the web
Origin binding: A credential usable only with the site it was registered for, enforced by the browser rather than the user.DEFINED IN Why a code sent to your phone does not stop phishing
Origin tag: A marker on a replicated change identifying where it came from, used to stop echo loops.DEFINED IN Two systems, one record
Orographic lift: The forced ascent of air over terrain.DEFINED IN Rain shadow
Orthographic depth: How consistently a writing system maps letters onto sounds.DEFINED IN Reading acquisition
Orthography: The conventional spelling system of a language, as distinct from its sounds or its grammar.DEFINED IN Spelling reform
Orthostatic intolerance: Dizziness or faintness on standing, here caused by reduced plasma volume after recumbency.DEFINED IN Bed rest harm
Osmosis: Movement of water across a membrane toward the more concentrated solution, which is how salt and sugar draw water out of a cell.DEFINED IN Food preservation
Osotua: A Maasai partnership in which requests made from genuine need are met if possible, without an accounted debt.DEFINED IN Herd dispersal among kin
Osteoblast: The cell that lays down new bone matrix, which subsequently mineralises.DEFINED IN Bone remodelling
Osteoclast: The multinucleated cell that dissolves bone mineral and digests matrix.DEFINED IN Bone remodelling
Osteocyte: A former osteoblast buried within the matrix, connected by fine processes; the skeleton's strain sensor.DEFINED IN Bone remodelling
Ostwald's rule of stages: The common tendency for the first solid formed to be the nearest in energy rather than the most stable one.DEFINED IN Disappearing polymorphs
Otolith organs: Inner-ear structures signalling linear acceleration and head tilt relative to gravity.DEFINED IN Motion sickness
Outbox table: A table in the service's own database holding messages waiting to be published, written in the same transaction as the business data.DEFINED IN The outbox
Outcome bias: Judging the quality of a decision or condition by how it happened to turn out rather than by the risk it carried.DEFINED IN Near misses
Outcome devaluation: The experimental test that distinguishes them, by making the reward unwanted and seeing whether the behaviour persists.DEFINED IN Habit formation
Outflow valve: The modulating vent, usually aft, whose opening sets how fast cabin air escapes and therefore what pressure is held.DEFINED IN Airplane cabin pressure
Outlier channel: An activation dimension whose values are consistently far larger than the rest, forcing a coarse shared scale on its whole tensor.DEFINED IN Model quantization
Outport: A newer deep-water port built downstream or seaward of an older one that can no longer take the ships.DEFINED IN Silted harbours
Outside option: The best alternative available to a worker elsewhere, which sets the point at which staying stops being worthwhile.DEFINED IN Who leaves first
Outside view: A forecast built from the distribution of outcomes of comparable past efforts.DEFINED IN Planning fallacy
Oven spring: The rapid final expansion in the first minutes of baking, before the crumb sets.DEFINED IN What makes bread rise?
Over-classification: Reflexively assigning the highest level, which inflates controls until people work around them.DEFINED IN Labelling before deciding
Over-fetching / under-fetching: Receiving more fields than needed, or needing several round trips to assemble one screen.DEFINED IN Letting callers ask for exactly what they want
Over-inclusive: Prohibiting conduct that does not raise the harm the rule was aimed at.DEFINED IN Bright-line rules
Over-provisioning: Flash the host cannot address, reserved to keep reclaimed blocks from being nearly all live.DEFINED IN Write amplification
Over-triage: Assigning a higher priority than the injuries warrant, consuming capacity needed elsewhere.DEFINED IN Emergency triage
Overdiagnosis: Correct diagnosis of disease that would never have caused symptoms or death in that person's lifetime.DEFINED IN Overdiagnosis
Overjustification effect: The reduction in later voluntary engagement after an activity has been performed for a promised external reward.DEFINED IN Paying pupils to read
Overlap: Deliberately repeating text at the end of one chunk and the start of the next, so an answer spanning a boundary still appears whole somewhere.DEFINED IN Chunking
Overlapping generations: A population in which cohorts are not synchronised, so every life stage is present at once.DEFINED IN Pantry moth persistence
Overlapping subproblems: The property that a recursion asks the same question many times, which is what memoization exploits.DEFINED IN Remembering the sub-answers
Overtrading: Growing faster than the business can fund the working capital growth requires.DEFINED IN Profit versus cash
Overtraining syndrome: A long-lasting decrement persisting despite rest, diagnosed only by excluding other causes.DEFINED IN Overtraining
Overuse injury: Damage from accumulated repetition rather than a single event, concentrated at growth plates and tendon attachments in young athletes.DEFINED IN Early sport specialization
Oxisol: A deep, highly weathered tropical soil dominated by iron and aluminium oxides and low in weatherable minerals.DEFINED IN Dust-fed rainforests
Oxygen bleach: Sodium percarbonate and similar solids releasing hydrogen peroxide; in powders, not liquids.DEFINED IN Washing machine odour
Oxygen diffusion barrier: A variable-permeability layer in the nodule cortex that sets how much oxygen enters the fixing zone.DEFINED IN Leghemoglobin in root nodules

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P and S waves: The fast compressional wave and the slower shear wave; the delay between them gives distance, and the head start gives early warning.DEFINED IN Why do earthquakes happen?
P wave: The faster, compressional body wave, which travels through solids and fluids alike.DEFINED IN Seismic shadow zone
PACELC: Daniel Abadi's 2012 extension: if partitioned, trade availability against consistency; else, trade latency against consistency.DEFINED IN The CAP theorem
Packing: Concentrating opposing voters into few districts so their surplus votes elect no one.DEFINED IN District boundaries
Page / erase block: The smallest unit of flash that can be programmed, and the much larger unit that must be erased together.DEFINED IN Write amplification
Page fault: The interruption raised when a program touches a page of memory not currently in a physical frame.DEFINED IN Memory thrashing
Pairwise comparison: A check between two members of a set; a group of n has n(n-1)/2 of them.DEFINED IN Birthday problem
Palimpsest: A site plan in which structures from many periods are visible together, having accumulated rather than coexisted.DEFINED IN Ancient population estimates
Paradox of tolerance: Popper's observation that unlimited tolerance tends to destroy tolerance, since it protects those who would abolish it.DEFINED IN Paradox of tolerance
Paradoxical intention: A clinical technique of instructing a person to attempt the opposite of the desired state, removing the effort that sustains the problem.DEFINED IN Self-defeating aims
Paraesthesia: An abnormal sensation such as tingling or prickling arising without an external stimulus.DEFINED IN Pins and needles
Parafoveal preview: Partial processing of the word ahead of the current fixation, using low-detail side vision.DEFINED IN Legibility
Parallax: The apparent shift of a nearby star against distant background over six months, giving distance by trigonometry alone.DEFINED IN Cosmic distance ladder
Parallel change (expand and contract): Adding the new form alongside the old, migrating callers, then removing the old form.DEFINED IN Backward compatibility
Parallel cousin: The child of a parent's same-sex sibling, and in unilineal systems typically a group-mate classed as a sibling.DEFINED IN Cross-cousin marriage · Merged kinship terms
Parallel run: Operating old and new on the same inputs at once, using only the old system's output.DEFINED IN Running both and comparing
Parameter-efficient adaptation: Capturing a task in a small set of additional weights beside an unchanged base model.DEFINED IN Foundation model economics
Parameters: Handshape, location, movement, orientation and non-manual marking; the contrastive building blocks of a sign.DEFINED IN Sign language
Parasitism: An association in which one partner's gain comes at the other's expense.DEFINED IN Symbiosis
Parent material: The rock or deposit a soil develops from, which sets its mineral starting point.DEFINED IN Soil formation
Parent-document retrieval: Indexing small pieces for matching but returning the larger section they belong to.DEFINED IN Chunking
Parent-offspring conflict: Trivers's argument that an offspring is selected to demand more investment than a parent is selected to give, because they value future siblings differently.DEFINED IN Infant night waking
Parental investment: The resources a parent spends on an offspring, and the true currency of the sex-ratio equilibrium.DEFINED IN Balanced sex ratios
Parity bit: One added bit making the count of ones in a block even or odd; detects an odd number of errors but locates none.DEFINED IN Error-correcting codes
Part-time penalty: The lasting loss of earnings and progression that follows reducing working hours, beyond the pay forgone at the time.DEFINED IN Caregiving load
Partial: One of the component frequencies a real tone contains; for strings and voices these are close to whole-number multiples of the lowest.DEFINED IN Musical consonance
Partial coalescence: Two fat globules sticking and fusing incompletely because crystals inside them prevent a full merge.DEFINED IN Butter from cream
Partial order: A relation holding between some pairs and not others; here, only between an item and its ancestors.DEFINED IN Half-sorted is enough · Order from pairwise rules
Partial pressure of oxygen: The share of ambient pressure due to oxygen, the force driving it into the blood.DEFINED IN Altitude training
Partible inheritance: The division of a holding among several heirs, which fragments parcels over generations regardless of anyone's intentions.DEFINED IN Scattered strip farming
Partition: The slice of an output a single run owns, usually a date, which is what a safe run replaces in whole.DEFINED IN Backfilling a pipeline · Delivered versus retained · Group-stage tiebreaks · Order within a slice · The CAP theorem
Partition key: The field hashed to choose a partition, and therefore the thing whose event order is actually protected.DEFINED IN Order within a slice
Partition pruning: Excluding whole partitions from a scan because the query's filter provably cannot match them.DEFINED IN Partition pruning
Partitionable work: Work that divides into independent pieces with few interfaces, and so does speed up with more people.DEFINED IN Coordination cost
Partitioning: Physically dividing a table by column values so queries can skip whole directories.DEFINED IN The small files problem
Parts pairing: Software that binds a component to a specific unit, so an otherwise genuine replacement part is refused.DEFINED IN Repair economics
Party discipline: The pressure that makes legislators vote with their party, and the usual route by which a formal separation loses its practical force.DEFINED IN Why do democracies separate powers?
Pascal: The SI unit of pressure; the atmosphere is around a hundred thousand of them, and theDEFINED IN Shower curtain drift
Pass-through: The share of a tax that shows up as a higher price to the other side.DEFINED IN Tax incidence
Passionate love: Berscheid and Hatfield's term for intense, absorbing, arousal-laden longing for union with another.DEFINED IN Fading attraction
Passivation: A thin, adherent oxide film that blocks further reaction, as on aluminium and stainless steel.DEFINED IN Corrosion · Passivation · Reinforced concrete
Past hypothesis: The added assumption that the universe began in a state of very low entropy, needed to give statistical mechanics a direction in time.DEFINED IN Irreversibility
Pasteurisation: A heat treatment that destroys pathogens and reduces spoilage organisms, without producing a sterile product.DEFINED IN Milk spoilage after opening · Pasteurised mushroom substrate
Patch embedding: Turning a small square crop of an image into a single vector, the image equivalent of a token embedding.DEFINED IN Multimodal fusion
Paternity uncertainty: The asymmetry that maternity is directly observable at birth while paternity historically was not, leaving the father-child link inferred.DEFINED IN Grandparent asymmetry
Path dependence: The tendency of an arrangement to persist because the cost of changing it rises with everything built on top of it.DEFINED IN Borders · Build cache geometry · Built never to be rebuilt · Canon formation · Exonyms · Persistent rules
Path integration: Keeping a running estimate of your position from your own movement, unaided by landmarks.DEFINED IN Wayfinding
Path length: How much air the light crosses before reaching you, far greater for a low sun.DEFINED IN Why is the sky blue?
Pathfinder: A small party dropped ahead of the main force to mark the zone, the direct countermeasure to dispersion.DEFINED IN Airborne drop dispersion
Patina: The accumulated surface changes of age and use, from chemical layers such as oxidation and tarnish to localised wear.DEFINED IN Patina and age value
Peak height velocity: The moment of fastest growth in the adolescent spurt, used as a datum from which maturity is measured forward and back.DEFINED IN Junior champions
Peak-end rule: The finding that a remembered evaluation approximates the average of the most intense moment and the final moment.DEFINED IN Remembered holidays
Peak-load pricing: Charging more in the period of concentrated demand, because that period must fund capacity used all year.DEFINED IN Tourism seasonality
Peer effect: The experimentally demonstrated increase in adolescent risk-taking when peers are present, absent in adults.DEFINED IN Adolescent risk
Pelog: A seven-tone system with unequal steps, from which subsets are drawn.DEFINED IN Gamelan tuning
Pentimento: A change of mind by the painter, painted over at the time, that later becomes visible or detectable.DEFINED IN Emerging pentimenti
Per-group scaling: Giving each small block of weights its own scale factor, so one extreme value cannot set the units for the entire tensor.DEFINED IN Model quantization
Perceptual load: How much of the available capacity the primary task consumes; higher load, less noticing.DEFINED IN Inattentional blindness
Perfidy: Killing, injuring or capturing an adversary by inviting and then betraying his confidence that one is entitled to protection.DEFINED IN Combatant identification
Performative utterance: A saying that constitutes the act rather than describing it, as promising and apologising do.DEFINED IN Apology and repair
Perihelion and aphelion: The closest and farthest points of Earth's orbit, reached in early January and early July.DEFINED IN Seasons
Period: The number of values a generator emits before its sequence repeats.DEFINED IN Pseudorandomness
Periodic market: A market held on fixed recurring days, serving a catchment too thin for a permanent shop.DEFINED IN Market day rotation
Periosteum: The vascular sleeve around a bone, a major source of the progenitor cells that build a fracture callus.DEFINED IN Cartilage healing
Peripheral chemoreceptors: The carotid and aortic bodies, which sense arterial oxygen pressure and respond strongly only when it is low.DEFINED IN Breathing urge
Peripheral tolerance: Suppression or switching-off of self-reactive cells that reach the tissues, chiefly by regulatory T cells and anergy.DEFINED IN Autoimmunity
Perirhinal cortex: A medial temporal region associated more with the familiarity signal than with contextual retrieval.DEFINED IN Deja vu
Peritrope: The "turning about" of a doctrine against itself, as Socrates applies it to Protagoras.DEFINED IN Self-refuting claims
Permafrost: Ground remaining at or below zero degrees Celsius for at least two consecutive years.DEFINED IN Pingo growth
Permanent hardness: Hardness carried as sulfates and chlorides, unaffected by boiling.DEFINED IN Limescale
Permanent wilting point: The soil water content below which a plant cannot extract water fast enough to recover overnight.DEFINED IN Irrigation scheduling depth
Permission-aware retrieval: Indexing that preserves each item's access list so search results can be filtered by the identity of the asker.DEFINED IN Data leakage paths
Permutation: One particular ordering of a set of objects.DEFINED IN Factorial explosion
Permutation equivariance: The property that reordering the inputs reorders the outputs identically, which attention has and language does not.DEFINED IN Transformer parallelism
Permutation symmetry: The fact that reordering hidden units yields a different parameter set computing the identical function.DEFINED IN Copying something you can only question
Perpetual problem: A recurring conflict rooted in an enduring difference of personality, need, or value, which is managed rather than resolved.DEFINED IN Proxy arguments
Persisted query: A query registered with the server ahead of time and invoked by identifier, restoring a finite request set.DEFINED IN Letting callers ask for exactly what they want
Persistence ignorance: The property of a domain class having no reference to, or knowledge of, how it is stored.DEFINED IN Objects that do not know they are stored
Persistent data structure: An immutable structure whose new versions share unchanged parts with the old, making updates cheap.DEFINED IN Immutability
Persister cell: A transiently non-growing ordinary cell that survives antibiotics by tolerance, with no spore structure and no inherited resistance.DEFINED IN Bacterial dormancy
Person-affecting principle: The claim that an act can be wrong only if it is worse for some particular individual.DEFINED IN Non-identity problem
Personal domain: The set of issues a person treats as their own preference to settle, with no claim on anyone else.DEFINED IN Adolescent-parent conflict
Pessimism / optimism about moral testimony: The two families of view on whether pure moral deference is defective.DEFINED IN Taking moral advice on trust
Pesticide treadmill: The self-reinforcing cycle in which each treatment makes the next one more necessary.DEFINED IN Pest resurgence
Peter principle: The proposition, from Peter and Hull's 1969 book, that people are promoted until they reach a role they perform badly, and then remain there.DEFINED IN Promotion mismatch
pH 4.6: The acidity threshold below which Clostridium botulinum does not grow, and the line between water-bath and pressure canning.DEFINED IN Food preservation
Phantom read: A re-run query returning rows that appeared after the transaction began.DEFINED IN Isolation levels
Pharmacodynamic tolerance: Reduced response at the target, through receptor desensitisation, internalisation or downstream counter-adaptation.DEFINED IN Drug tolerance
Pharmacokinetic tolerance: Reduced drug exposure through faster metabolism, typically by induced liver enzymes.DEFINED IN Drug tolerance
Phase inversion: The swap in which the dispersed phase becomes the continuous one, as fat does when cream becomes butter.DEFINED IN Butter from cream
Phase inversion on reflection: The half-wavelength flip a wave acquires reflecting off a higher-index medium; here it happens at both faces and so cancels out.DEFINED IN Anti-reflective coating · Soap film colours
Phase margin: How much further phase lag a loop could tolerate at its crossover frequency before oscillating.DEFINED IN Measurement dead time
Phase response curve: The direction and size of the shift a stimulus produces, plotted as a function of the internal phase at which it arrives.DEFINED IN Dawn light and the body clock · Jet lag
Phase-cut dimming: Reducing light by blocking part of each mains half-cycle rather than by lowering the voltage.DEFINED IN LED dimmer incompatibility
Phasing orbit: A temporary orbit of a different period, flown to change one craft's angular position relative to another.DEFINED IN Orbital rendezvous
Pheromone: A chemical signal released by one animal that changes the behaviour of others of its species.DEFINED IN Collective ant behavior
Pheromone trap: A lure emitting synthetic sex pheromone to catch males; a monitoring instrument rather than a control measure.DEFINED IN Pantry moth persistence
Phi phenomenon: Wertheimer's pure movement percept at short intervals, in which motion is experienced without any object being seen to move.DEFINED IN Apparent motion
Phoneme: The smallest sound unit that distinguishes words in a language, inferred rather than heard as separate.DEFINED IN Reading acquisition
Phoneme restoration: The effect in which a speech sound masked by noise is heard as present, and the noise cannot be located.DEFINED IN Transcribed speech
Phonemic awareness: The ability to notice and manipulate a spoken word's individual phonemes.DEFINED IN Reading acquisition
Photoperiod: The day length a plant uses as a cue for when to flower, which varies with latitude and season.DEFINED IN East-west diffusion
Photorespiration: The wasteful salvage pathway triggered when RuBisCO grabs oxygen, worse in heat and drought.DEFINED IN Photosynthesis
Photosphere: The layer of a star from which visible light finally escapes.DEFINED IN Star colors
Phreatic passage: One dissolved below the water table, in fully flooded conditions, typically tubular.DEFINED IN Cave formation
Phrenic nerve: The nerve supplying the diaphragm, arising from cervical segments C3 to C5.DEFINED IN Referred pain
Physical ageing: Slow densification toward equilibrium below the transition, with no chemical change.DEFINED IN Physical ageing of plastics
Physical dependence: The adapted state whose unmasking on stopping produces a withdrawal syndrome.DEFINED IN Drug tolerance
Physical model: The implementation on a specific platform: tables, datatypes, indexes, partitioning, and deliberate denormalisation.DEFINED IN Drawing the same model three times
Phytochrome: The plant pigment that senses the red to far-red ratio and so detects nearby foliage.DEFINED IN Forest height race
PID 1: The first process in a process namespace, for which the kernel does not apply default signal actions.DEFINED IN The first process
Pidgin: A contact variety with a restricted vocabulary and no consistent grammar, nobody's first language.DEFINED IN Creole genesis
Piedmont: The belt of older, harder rock lying inland of the coastal plain.DEFINED IN Fall-line cities
Pigeonhole principle: If there are more keys than slots, some slots must receive more than one key.DEFINED IN Finding without searching · Pigeonhole principle
Pikuach nefesh: The rabbinic principle that preserving human life overrides sabbath restrictions.DEFINED IN Mandated rest days
Pilling-Bedworth ratio: The volume of oxide formed divided by the volume of metal consumed, a necessary but not sufficient test of whether a film can cover the surface.DEFINED IN Passivation
Pioneer species: A fast-growing, light-demanding, widely dispersed species that establishes on newly opened ground.DEFINED IN Ecological succession
Pipeline stock: Inventory in transit between points, as distinct from stationary stock held at rest.DEFINED IN Cross-docking
Piriform cortex: The primary olfactory cortex, reached from the bulb without an obligatory thalamic relay.DEFINED IN Smell and memory
Pit organ: A facial chamber spanned by a thin, air-backed membrane that warms when infrared radiation falls on it.DEFINED IN Pit viper infrared sensing
Pitch point: The fixed point on the line of centres through which the contact normal must pass.DEFINED IN Involute gear teeth
Pitting corrosion: Localised breakdown of a passive film, typically initiated by chloride, producing deep narrow holes with little overall mass loss.DEFINED IN Passivation
Pivot: The element a partition step compares everything against; its rank determines how balanced the split is.DEFINED IN Shuffling before sorting
Pivotal (or critical) party: One whose departure would turn a winning coalition into a losing one.DEFINED IN Coalition formation
pKa: The pH at which a weak base is half protonated; it fixes the balance between the two forms at any given pH.DEFINED IN Local anaesthetic failure
PKCE (Proof Key for Code Exchange): RFC 7636, the mechanism binding an authorization code to the client instance that requested it.DEFINED IN Proving you started the exchange you are finishing
Plan: The computed difference between declared and observed state, shown before it is applied.DEFINED IN Declaring the destination, not the route
Planck feedback: The increase in outgoing radiation as a surface warms; weaker in cold regions, so the same forcing produces more warming there.DEFINED IN Polar amplification
Plane of incidence: The plane containing the incoming ray and the normal to the surface, against which the two polarisation components are defined.DEFINED IN Brewster angle glare
Planform alignment: Aligning leading and trailing edges onto a few shared headings so returns concentrate into a small number of narrow bearings rather than spreading.DEFINED IN Stealth tradeoff
Planned obsolescence: The deliberate design or marketing of a product so that it is superseded on a schedule rather than when it fails.DEFINED IN Fashion churn · Warranty timing
Plant-available water: The difference between those two, usually in millimetres per metre of soil depth.DEFINED IN Irrigation scheduling depth
Plant-soil feedback: The net effect a plant has on its own performance through the soil community it cultivates; negative here, positive in some other systems.DEFINED IN Janzen-Connell seedling mortality
Plasma frequency: The natural oscillation rate of free electrons about their ions, sqrt(n e²/ε₀ m_e)/2π, above which a plasma transmits and below which it reflects.DEFINED IN Low-frequency radio cutoff
Plasma volume expansion: An early increase in the fluid portion of blood following repeated heat exposure.DEFINED IN Heat acclimatization
Plasmid: A small loop of DNA separate from the chromosome, often carrying several resistance genes and transferable between cells.DEFINED IN Antibiotic course length · How does antibiotic resistance develop?
Plateau: A stretch of practice during which the measured performance does not improve, bounded by periods in which it does.DEFINED IN Learning plateaus · Radiocarbon calibration plateaus
Play signal: A marker such as a canine play bow or a relaxed open-mouth face that announces the behaviour that follows is not in earnest.DEFINED IN Children's play
Playa: The flat, salt-crusted floor of a terminal basin that holds water only intermittently.DEFINED IN Endorheic basins
Pluralistic ignorance: Everyone privately doubting while publicly appearing calm, so each reads the others' composure as reassurance.DEFINED IN Bystander effect · The silent classroom
Plurality: The candidate with the most first preferences wins, regardless of majority.DEFINED IN Voting rules
Pneumatic skeleton: Bone invaded by air sacs, as in birds and sauropods, reducing mass for a given size.DEFINED IN Land size limits
Poincare-Hopf theorem: The indices of a continuous tangent field's zeros sum to the surface's Euler characteristic.DEFINED IN Hairy ball theorem
Point bar: The deposit built on the inside of a migrating bend, the physical signature of accretion.DEFINED IN River boundaries that shift · River meanders
Point transfer: A copying method that measures fixed points on a model and reproduces their depths in a new block.DEFINED IN Marble supports
Point-biserial correlation: The correlation between choosing an option and total score; positive for a good key, negative for a good distractor.DEFINED IN Diagnostic distractors
Point-in-time join: A join that matches a record to the version of an entity whose validity interval contains the record's timestamp.DEFINED IN Point-in-time joins
Point-on-wave switching: Controlled closing timed to the supply waveform, chosen to avoid a flux offset.DEFINED IN Transformer inrush
Pointer chasing: A chain of loads where each address is only known once the previous load returns, preventing overlap.DEFINED IN Fewer operations, slower program
Poison message: A message that fails every time it is processed, so redelivery can never resolve it.DEFINED IN Poison messages
Poisson noise: The intrinsic fluctuation of a random count, equal to the square root of the count.DEFINED IN Sky-background limit
Polar stratospheric cloud: Particles of nitric acid and water forming only in the extreme cold of the polar winter stratosphere, providing the surfaces on which chlorine is released.DEFINED IN Antarctic ozone hole
Polar vortex: The ring of strong winter westerlies that isolates the air over a pole from mid-latitude air.DEFINED IN Antarctic ozone hole
Policy binding: Attaching controls to the label rather than to individual records, so new data is governed on arrival.DEFINED IN Labelling before deciding
Policy decision point (PDP): The component that evaluates policy against the request and its attributes and returns an outcome.DEFINED IN Deciding apart from enforcing
Policy enforcement point (PEP): The component sitting on the request path that blocks or permits, and carries out any obligations attached to a decision.DEFINED IN Deciding apart from enforcing
Policy information point (PIP): A source of attributes the decision point queries, such as a directory or device registry.DEFINED IN Deciding apart from enforcing
Political appointee: An official serving at the pleasure of the government of the day.DEFINED IN Civil service tenure
Politicisation of intelligence: Distortion of assessment by the policy preferences of its recipients, usually through selective attention rather than falsification.DEFINED IN Unusable intelligence
Pollen coupling: The feedback by which wind-pollinated neighbours flowering together fertilise each other better, tending to synchronise them.DEFINED IN Mast seeding
Pollination syndrome: A recurring suite of floral traits statistically associated with one class of pollinator.DEFINED IN Pollination specificity
Pollinator effectiveness: Pollen actually deposited on a receptive stigma per visit, as distinct from visitation rate.DEFINED IN Managed hives and wild pollinators
Poloidal and toroidal field: Respectively the pole-to-pole component and the component wound around the rotation axis.DEFINED IN Solar cycle
Polya's theorem: The 1921 result that the simple symmetric lattice walk is recurrent in one and two dimensions and transient in three or more.DEFINED IN Random walk recurrence
Polycomb complexes: Protein assemblies that place repressive chromatin marks and maintain them through cell division.DEFINED IN Vernalization
Polymerisation: The joining of many small molecules into a large networked one; here, fatty acid chains linking into a solid film.DEFINED IN Cast-iron seasoning · Setting a stain
Polymorph: One of several distinct crystal packings of the same compound, differing in physical properties but not in chemistry.DEFINED IN Disappearing polymorphs
Polynya: An area of open water kept ice-free within the ice pack, here by winds pushing new ice away as fast as it forms.DEFINED IN Sea-ice brine rejection
Polyphenol oxidase: The enzyme that oxidises phenolic compounds to quinones, which polymerise into dark pigments.DEFINED IN Chilling injury in fruit
Popularity bias: The tendency of a recommender to over-recommend already-popular items, because they carry more and better-measured feedback.DEFINED IN Recommendation narrowing
Pore close-off: The depth at which pore spaces pinch shut and air is finally sealed into bubbles.DEFINED IN Ice core records
Port: An interface declared by the domain describing what it needs from the outside world, in the domain's own vocabulary.DEFINED IN Dependency direction
Portal circulation: The venous system carrying blood from the gut to the liver before it joins the general circulation.DEFINED IN First-pass metabolism
Positional encoding: An added signal telling the model where each token sits, since parallel processing discards order.DEFINED IN Transformer parallelism
Positional good: Something whose value depends on how much you have relative to others, so general effort to obtain it cancels out.DEFINED IN Mandated rest days
Positional information: The cells' encoding of where along a structure they sit, which determines what gets rebuilt.DEFINED IN Limits of regeneration
Positive feedback: An arrangement where an outcome increases the tendency that produced it.DEFINED IN Collective ant behavior
Positive passenger bag match: The operational name for that check, performed at flight close-out.DEFINED IN Baggage reconciliation
Positive predictive value: Of those testing positive, the fraction who truly have the condition; depends on prevalence, not on the test alone.DEFINED IN Screening false positives
Positive recurrence: Return to a state is certain with finite expected waiting time; π is the reciprocal of that time.DEFINED IN Long-run chain behaviour
Positivity effect: The tendency, associated with shorter horizons, to favour positive over negative material in attention and memory.DEFINED IN Shrinking social circles
Post-enumeration survey: An independent re-canvass of sampled addresses, used to estimate how many people the census missed.DEFINED IN Census undercount
Post-filtering: Removing unauthorised results after ranking has been computed over the full corpus.DEFINED IN Permission-aware retrieval
Postcondition: What the routine guarantees on return, given that the precondition held.DEFINED IN Design by contract
Posterior: The revised probability after the evidence, which becomes the prior for the next update.DEFINED IN Bayesian updating
Postings list: The list of documents, and often positions, recorded for a single term.DEFINED IN Search indexing
Potential temperature: A parcel's temperature adjusted to a reference pressure, unchanged by adiabatic ascent or descent.DEFINED IN Katabatic winds
Power index: A measure of bargaining strength built from how often a party is pivotal, rather than from how many seats it holds.DEFINED IN Coalition formation
Power law of practice: The observation that group-average performance improves as a decelerating function of the number of trials.DEFINED IN Learning plateaus
Power-to-weight ratio: Sustainable power divided by total mass, in watts per kilogram; theDEFINED IN Climbing versus descending weight
Poynting-Robertson drag: The small tangential drag caused by aberration of absorbed sunlight in a moving grain's frame, which shrinks its orbit.DEFINED IN Zodiacal dust replenishment
Pozzolan: A reactive silica-bearing material, such as volcanic ash or fly ash, that converts lime into further hydrate.DEFINED IN Cement hardening
Practice conception of rules: Rawls's view that where an act is defined by a practice, the justification of the practice cannot be reused to justify departing from it.DEFINED IN Promising
Pragmatics: How meaning depends on context and inferred intention rather than on the literal words.DEFINED IN Text message tone
Pragnanz: The Gestalt claim that perception settles on the simplest and most regular organisation the input allows.DEFINED IN Visual grouping
Pre-delegation: Authority to release weapons written down in advance for named subordinates under stated conditions, so no live order is required.DEFINED IN Delegated launch authority
Pre-filtering (predicate pushdown): Evaluating the access predicate during the search itself, so unauthorised items are never candidates.DEFINED IN Permission-aware retrieval
Pre-metastatic niche: A distant tissue altered by signals from the primary tumour before any tumour cell arrives.DEFINED IN Metastasis
Pre-registration: Committing to hypotheses and analysis before collecting data, which removes the flexibility that inflates published effects.DEFINED IN Decision fatigue
Prebunking (inoculation): Pre-emptively exposing people to a weakened form of a misleading argument so they resist the full version later.DEFINED IN Persistence of misinformation
Precession: The slow sweep of a spinning body's axis around another axis, caused by a torque perpendicular to its angular momentum.DEFINED IN Gyroscopic precession
Precipitation: The falling of a dissolved substance out of solution as a solid when conditions change.DEFINED IN Limescale
Precisification: One admissible way of sharpening a vague predicate that respects all the clear cases.DEFINED IN Vagueness
Precision (positive predictive value): The share of alerts that correspond to a real condition; it collapses when the condition is rare, even for a very accurate detector.DEFINED IN Alert fatigue
Precommitment: Binding your future self in advance so the tempting option is unavailable when the moment comes.DEFINED IN Weakness of will · Why do we procrastinate?
Precondition: What a caller must guarantee before invoking a routine; its violation is the caller's bug.DEFINED IN Design by contract
Predator satiation: Producing so much seed at once that consumers cannot take it all, made possible by lean years that keep their numbers low.DEFINED IN Mast seeding
Preference falsification: Publicly misrepresenting one's private views under social or political pressure, hiding the true distribution of opinion.DEFINED IN Revolution timing
Preference revelation problem: The difficulty that people have incentives to misstate how much a public good is worth to them.DEFINED IN Compulsory taxation
Preference reversal: A change in which of two fixed options is preferred, caused only by moving both further off.DEFINED IN Delay discounting · Weakness of will · Why do we procrastinate?
Preference uncertainty: Not knowing what one wants until after comparing, leaving no yardstick for stopping.DEFINED IN Choice overload
Prefetching: Hardware fetching data ahead of the program once it detects a predictable access pattern.DEFINED IN Fewer operations, slower program
Prefill: The initial parallel pass over every prompt token, which also populates the cache.DEFINED IN Prefill and decode · Time to first token
Prefix code: A code in which no codeword is the start of another, so a stream decodes unambiguously.DEFINED IN Lossless compression
Prefix sharing: The property that keys with a common beginning traverse and occupy the same nodes.DEFINED IN Words stored by their beginnings
Preflight: An automatic OPTIONS request the browser sends first for non-simple requests, to ask permission before the real one.DEFINED IN CORS in the web
Preload: The tension locked into a bolt on assembly, balanced by an equal compression in the clamped members.DEFINED IN Bolt preload
Premature closure: Settling on the first plausible explanation and ceasing to look; recognition's failure mode.DEFINED IN Skilled diagnosis
Premise: A claim offered as a reason for a conclusion.DEFINED IN What makes an argument logically valid?
Premium: The sum paid by an apprentice's family to the master at the outset.DEFINED IN Apprenticeship indentures
Prepared state: The durable condition of a participant that has voted yes, holds its locks, and can no longer decide the outcome alone.DEFINED IN The blocking commit
Prerequisite chain: A run of topics in which each takes the previous one's mastery as an input, so a break propagates forward.DEFINED IN Prerequisite chains
Present bias: The tendency to weigh immediate costs and rewards far more heavily than future ones.DEFINED IN Why do we procrastinate?
Presentation (exposure) bias: Distortion arising because feedback exists only for items the system chose to display.DEFINED IN Recommendation narrowing
Pressure drag: The rearward force from unrecovered pressure behind a body, dominant for blunt shapes.DEFINED IN Golf ball dimples
Pressure gradient force: The push from high toward low pressure, perpendicular to the isobars and stronger where they are closer together.DEFINED IN Geostrophic wind
Pressure microphone: Diaphragm sealed at the back, responding to absolute pressure at a point; omnidirectional, no proximity effect.DEFINED IN Microphone proximity effect
Pressure-gradient microphone: Open on both faces, responding to the pressure difference across the diaphragm; directional by construction.DEFINED IN Microphone proximity effect
Pressure-independent terminal: A box that measures and holds its own flow.DEFINED IN Air balancing
Presumption: The position treated as holding by default until displaced.DEFINED IN Burden of proof
Presumption of innocence: The rule that an accused is treated as innocent until proved otherwise.DEFINED IN Presumption of innocence
Prevailing wind: The direction from which wind most frequently blows at a place, westerly across most of north-west Europe.DEFINED IN Windward wealth divide
Prevalence (base rate): The fraction of the tested population that actually has the condition.DEFINED IN Screening false positives
Preventive check: Malthus's term for population restraint acting through fewer births, as against the positive check of higher mortality.DEFINED IN Late marriage and population restraint
Price discrimination: Charging different effective prices to different buyers, here by metering use through the consumable.DEFINED IN Aftermarket pricing · Different prices, same room
Price ending: The final digits of a price, treated here as a signal in its own right rather than as part of the amount.DEFINED IN Charm pricing
Price signal: The information conveyed by a price change about relative scarcity, prompting adjustment without transmitting its cause.DEFINED IN Price signals
Price structure: How a platform's total margin is divided between its two sides, as distinct from the total itself.DEFINED IN Two-sided market launch
Prima facie duty: Ross's term for a real duty that can be outweighed by another without ceasing to have been a duty.DEFINED IN Promising
Primary clustering: Linear probing's tendency to build contiguous runs that grow faster the longer they already are.DEFINED IN Hash table clustering
Primary dormancy: A block to germination established in the seed before it is shed from the parent plant.DEFINED IN Weed seed banks
Primate city: A country's largest city when it is disproportionately larger than the second, often the very outcome a compromise capital was meant to avoid.DEFINED IN Compromise capitals · Primate cities
Prime: A whole number greater than 1 whose only positive divisors are 1 and itself.DEFINED IN Infinitude of primes
Primitive: One of the basic kinds of thing a protocol lets a server expose.DEFINED IN Control as a classification
Principal: The original amount you deposited.DEFINED IN Compound interest · The audit record as the product
Principal moments of inertia: The three numbers describing how hard a body is to spin about each of three perpendicular axes through its centre of mass.DEFINED IN Intermediate axis instability
Principal-agent problem: The difficulty of getting an agent to act for a principal whose interests they do not share and whose actions the principal cannot fully observe.DEFINED IN Board independence
Principle of continence: Davidson's requirement that one's action-guiding judgement follow one's all-things-considered judgement.DEFINED IN Weakness of will
Principle of contrast: The assumption that two different forms do not mean exactly the same thing, which pushes near-synonyms to differentiate.DEFINED IN Loanword doublets
Principle of distinction: The requirement that operations be directed only against combatants and military objectives.DEFINED IN Combatant identification
Principle of least astonishment: The design rule that a component should behave the way its intended users would predict, given the signals it emits.DEFINED IN Least astonishment
Prior: The probability assigned to a belief before the new evidence is considered.DEFINED IN Bayesian updating · Faith and evidence · Fog of war · Visual grouping
Prior shift: The base rate of the outcomes changes, altering what a given score implies.DEFINED IN Model drift
Priority effect: The influence of arrival order on which community establishes, operating through pre-emption of resources or modification of conditions.DEFINED IN Gut colonization order · Pasteurised mushroom substrate
Private information with incentive to misrepresent: Each side knows its own strength and resolve and profits by overstating them, so its claims are discounted.DEFINED IN Peace negotiation
Private key: A secret key only you hold, used to decrypt (the door key).DEFINED IN How encryption keeps messages secret
Private signal: The individual, non-public evidence a person holds about which option is better.DEFINED IN Traveler herding
Privilege separation: Keeping the component that decides apart from the component permitted to act.DEFINED IN Tool calling boundary
Procedural justice: Fairness in how a decision is made rather than what it decides; Tyler's research finds it drives legitimacy more than outcomes do.DEFINED IN Everyday legal compliance
Proceduralisation: The compiling of separately controlled steps into a single routine that runs without step-by-step supervision.DEFINED IN Choking under attention
Process loss: Steiner's term for the gap between what a group's members could jointly produce and what the group actually produces.DEFINED IN Group projects
Process safety: The management of low-frequency, high-consequence hazards, distinct from the personal-injury statistics often used as a proxy for it.DEFINED IN Near misses
Processing fluency: The subjective ease with which information is taken in; easier-processed material is judged more true, more familiar and more likeable.DEFINED IN Accent and perceived competence · Fluency illusion · Typeface voice
Processing time: The moment an event reaches the system that handles it; dependent on network and retry behaviour.DEFINED IN Event time versus arrival time
Prodrug: An inactive molecule that must be converted in the body before it works; aciclovir is converted mainly by a viral enzyme.DEFINED IN Antiviral difficulty
Product quantisation: Splitting a vector into sub-vectors and storing each as a codebook index, shrinking memory sharply.DEFINED IN Approximate nearest neighbour search
Production blocking: The loss in idea generation caused by only one member being able to contribute at a time.DEFINED IN Group projects
Profit pool: The total profit available in an activity, which can be far smaller after a technological shift than before it.DEFINED IN Incumbent disruption
Progradation: The seaward advance of a shoreline as sediment builds new land out from it.DEFINED IN Silted harbours
Prograde / retrograde burn: Thrust along, or against, the direction of travel, raising or lowering the opposite side of the orbit.DEFINED IN Orbital rendezvous
Progress measure: A quantity computed from a model's internals that tracks partial assembly of a solution before performance metrics move.DEFINED IN Grokking in training
Project STAR: The randomised Tennessee experiment of the late 1980s assigning early-grade pupils to small or regular classes.DEFINED IN Tutoring versus class size
Projection: A derived, queryable view built by folding events; disposable and rebuildable.DEFINED IN Event sourcing · Separating the read model from the write model
Prolonged grief: Persistent, impairing grief well beyond the typical course; a minority pattern, not a late stage of the usual one.DEFINED IN Grief timing
Prompt: A user-controlled template a person deliberately invokes, typically from a menu or command.DEFINED IN Control as a classification
Prompt chaining: Decomposing a task into several sequential model calls, where each call's output becomes the next call's input.DEFINED IN Prompt chaining
Prompt critical: The condition in which prompt neutrons alone sustain the chain, so the delayed fraction no longer sets the timescale.DEFINED IN Critical mass
Prompt injection: Text inside supplied content that is read as an instruction and followed, overriding the developer's intent.DEFINED IN Delimiters as a boundary · System prompt priority · Tool calling boundary
Proof testing: Deliberately loading every unit above its service stress so flawed units fail before delivery.DEFINED IN Fibre strength and flaws
Properly basic belief: A belief justifiably held without being inferred from other beliefs, such as belief in other minds.DEFINED IN Faith and evidence
Proportional balancing: Setting branch flows as ratios first, then fixing the total at the fan.DEFINED IN Air balancing
Proportional division: Each of n participants values their own share at 1/n or more; envy-free division — no participant would prefer another's share.DEFINED IN Envy-free division
Proskynesis (veneration): Reverence that may be shown to an icon or relic, held to pass to its prototype.DEFINED IN Prohibition of images
Prosody: The pitch, rhythm, loudness and timing of speech, which carry attitude alongside the words.DEFINED IN Text message tone
Prospect-refuge: Appleton's proposal that people prefer positions offering an outlook while remaining sheltered; well supported as description, weakly as explanation.DEFINED IN Architectural atmosphere
Prospective timing: Judging a duration while it is happening.DEFINED IN Sense of time
Protease: An enzyme that cuts protein chains into smaller fragments, included in enzyme laundry detergents.DEFINED IN Setting a stain
Protected value: A value a person treats as resisting trade-off against other goods, money especially.DEFINED IN Pricing the sacred
Protective posture: A graded level of protection worn in anticipation of attack, from equipment carried up to full wear.DEFINED IN Chemical protective posture
Proto-cuneiform: The earliest Mesopotamian script phase, largely administrative and not yet recording language.DEFINED IN Writing invention
Protocol error: A failure of the exchange itself: unparseable message, unknown method, invalid parameters. No work was attempted.DEFINED IN Protocol errors versus execution errors
Protocol version: A number governing the message format and handshake structure itself, distinct from the features carried inside it.DEFINED IN Capability negotiation
Prototype: The person or reality an image depicts, and the intended destination of honour shown to it.DEFINED IN Prohibition of images
Protracted war: Mao's staged strategy of trading space and time to preserve a force until the balance shifts.DEFINED IN Asymmetric warfare
Proust effect: The popular name for odour-cued autobiographical memory, after the madeleine passage in Proust.DEFINED IN Smell and memory
Provenance: The documented chain of custody linking an object to its claimed origin.DEFINED IN A relic proved false · Documentation that points at its evidence · Photographic evidence · Planting the source it will cite · Value of the original · What an assistant should forget
Provisional sum: An allowance for work that cannot be priced until it is exposed, reconciled against actual cost later.DEFINED IN Quoting a job
Provisioned concurrency: Keeping instances initialised in advance so requests do not meet the cold path, paid for continuously.DEFINED IN Cold starts
Proxy: A measurable natural quantity standing in for a climate variable never directly recorded.DEFINED IN Tree-ring evidence · Wrapping without changing
Proxy evidence: An indirect trace standing in for a missing direct record, such as skeletal stress markers or serial parish registers.DEFINED IN Historical silence · Recovering a schedule nobody wrote down · Seating by the window · Wrong with nothing missing
Proxy measure: A quantity that stands in for the one you actually care about, accurate only while the relationship between them holds.DEFINED IN Progress-bar estimates
Prozbul: Hillel's device transferring private debts to a court so the seventh-year cancellation does not reach them.DEFINED IN Ritual legal fictions
Prudential issues: Matters of the actor's own safety and health, which parents typically treat as legitimately theirs and adolescents often treat as personal.DEFINED IN Adolescent-parent conflict
Pseudo-polynomial time: Running time polynomial in the numeric value of an input rather than in the number of bits used to write it.DEFINED IN Remembering the sub-answers
Pseudomorph: A cast of a decayed organic object formed in the corrosion products of adjacent metal, preserving weave or grain but not the material.DEFINED IN Preservation bias
Pseudorange: A measured satellite distance still containing the receiver's clock bias, which isDEFINED IN How does GPS find your location?
Psychological continuity: The chain of overlapping memory, intention and character that Locke, and later Parfit, took to carry personal identity.DEFINED IN Identity over change
Psychrotroph: An organism that grows well at refrigeration temperatures; the dominant spoilers of chilled fish are of this kind.DEFINED IN Fish spoiling fast · Milk spoilage after opening
Public client: A client that cannot hold a credential confidentially, such as a mobile or browser-based application.DEFINED IN Proving you started the exchange you are finishing
Public good: A benefit available to everyone in a group regardless of who paid for it, and therefore typically under-supplied.DEFINED IN The silent classroom
Public key: A freely shared key used to encrypt messages to you (the mail slot).DEFINED IN How encryption keeps messages secret
Public-key authentication: Proving identity by signing with a private key that the verifier checks using the corresponding public key.DEFINED IN A secret you never send
Publish-subscribe: A messaging arrangement in which producers send to a topic and consumers subscribe to it, with neither naming the other.DEFINED IN The publisher that knows no subscribers
Pupation site: The place a mature larva crawls to before pupating, which for these moths is structure rather than food.DEFINED IN Pantry moth persistence
Purchasing power: How much a unit of money can actually buy.DEFINED IN What is inflation?
Pure moral deference: Forming a moral belief solely on someone's say-so, without their reasons.DEFINED IN Taking moral advice on trust
Pycnocline: The depth at which density changes sharply, separating a light upper layer from a dense lower one and resisting mixing.DEFINED IN Coastal dead zones
Pygmalion effect: The specific claim, from Rosenthal and Jacobson's 1968 study, that induced teacher expectations raise pupil attainment.DEFINED IN Teacher expectations
Pyrogen: Any substance that raises the body's temperature set point.DEFINED IN Fever
Pyrolysis: The thermal breaking of large molecules into smaller fragments, which happens to wax vapour before it burns.DEFINED IN Candle wick

Q

Qualified one-way costs shifting: An arrangement protecting a losing claimant from paying the defendant's costs while a losing defendant is not protected.DEFINED IN Loser-pays cost rules
Quality factor (Q): The number of radians of oscillation over which a vibration's energy decays; large Q means very low loss per cycle.DEFINED IN Cracked bell tone
Quality-assuring premium: A price above cost that generates a rent stream a firm forfeits if caught cutting quality.DEFINED IN Brand advertising
Quantisation: Snapping recorded or programmed notes exactly onto that grid.DEFINED IN Groove and microtiming
Quantity surcharge: The case where a larger pack carries a higher unit price than a smaller one of the same product.DEFINED IN Unit-price inversion
Quarter-wave thickness: A film thickness of lambda/(4n), which puts the two surface reflections half a cycle apart.DEFINED IN Anti-reflective coating
Quasi-identifier: An attribute not identifying alone but identifying in combination, and only relative to some available outside dataset.DEFINED IN Re-identification of anonymized data
Quasi-voluntary compliance: Margaret Levi's term for taxpayers paying without individual coercion, sustained by belief the state is keeping its side.DEFINED IN Resource revenue and accountability
Query planner: The component that chooses whether and how to use an index for a given query.DEFINED IN Indexing
Query, key, value: The three projections of each position: what it seeks, how it advertises itself, and what it contributes when attended to.DEFINED IN Attention as a budget
Quiescent reserve: Stem cells held out of cycle, which survive an exposure and repopulate the tissue afterwards.DEFINED IN Chemotherapy selectivity
Quorum: The agreeing majority required by a consensus protocol before shared state may change.DEFINED IN Control plane and data plane · Distributed consensus · Quorums · Split-brain

R

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R0 (basic reproduction number): The average number of secondary infections one case causes in an entirely susceptible population.DEFINED IN Herd immunity
Racemic mixture: An equal mixture of both enantiomers, which is what an ordinary synthesis usually produces.DEFINED IN Molecular handedness
Radar cross-section: The effective area characterising how much energy an object returns toward the emitter; a property of shape, material, aspect angle and wavelength, not of physical size.DEFINED IN Stealth tradeoff
Radar signature: The combination of frequency, pulse length, repetition rate and scan pattern that identifies a particular set, and so the platform carrying it.DEFINED IN Emissions control
Radial velocity: The component of a source's motion directly along the line of sight, and the only component the classical shift depends on.DEFINED IN Doppler effect · Exoplanet detection
Radiation pressure: The force exerted by light's momentum, proportional to a grain's cross-section rather than its mass.DEFINED IN Comet tails
Radiative cooling: Net loss of energy from a surface emitting infrared faster than it receives it.DEFINED IN Radiation frost
Radiative zone: The region from the core out to about 0.7 solar radii, where energy moves by absorption and re-emission.DEFINED IN Photon escape time
Radix tree: A trie with unbranching chains collapsed into single edges carrying whole substrings.DEFINED IN Words stored by their beginnings
Railway time: The nineteenth-century practice of running all stations on one company's clock, the precursor of standard time.DEFINED IN Time zones
Rain shadow: The dry leeward side of a mountain range, where arriving air has already lost its moisture.DEFINED IN Desert latitudes
Rally effect: A temporary rise in support for a leadership perceived to be under external threat.DEFINED IN Blockade and resolve
RAM model: The standard abstract machine in which basic operations on a word cost one unit and memory access is constant time.DEFINED IN Counting steps instead of timing
Ram pressure: The pressure exerted on a body by the gas it drives into, which compresses and heats that gas ahead of it.DEFINED IN Meteor streaks
Ramp-up cost: The output lost while experienced people bring new arrivals up to speed.DEFINED IN Coordination cost
Random access: The ability to read position k in constant time, without traversing positions before it.DEFINED IN Halving the haystack
Random error: Variation with no consistent direction, which averaging reduces.DEFINED IN Error cancellation in averages
Random walk: A path of independent steps in random directions, whose net displacement grows as the square root of the number of steps.DEFINED IN Heat diffusion time · Photon escape time
Range: The greatest distance a customer will travel to a market, here bounded by a there-and-back day on foot.DEFINED IN Market day rotation · Town spacing
Rank-size rule: The empirical tendency for the nth largest city to be roughly 1/n the size of the largest.DEFINED IN Primate cities · Town spacing
Rapid intensification: Conventionally, an increase in maximum sustained wind of about 30 knots within 24 hours.DEFINED IN Hurricane intensification
Rate bucket: One of a discrete set of prices, opened and closed as the forecast changes, which is why rates move in jumps.DEFINED IN Shoulder-season price cliff
Rate coding: Grading force by how fast impulses arrive at an already-recruited motor unit.DEFINED IN Early strength gains
Rate fence: A restriction attached to a price that makes it unattractive to the buyers you want to charge more, so buyers sort themselves.DEFINED IN Different prices, same room
Rater severity: A marker's general tendency to score above or below the consensus, treated as an additive offset that moderation can remove.DEFINED IN Marker disagreement
Ratio decidendi: The reasoning essential to the outcome on the facts, and the only part that binds.DEFINED IN Legal precedent
Rational inattention: The idea that ignoring small decisions is itself an efficient use of limited attention, which is why the pattern is not simply irrational.DEFINED IN Subscription inertia
Rationality (plausibility) test: A diagnostic check that compares one in-range signal against others and against a model, rather than testing the circuit itself.DEFINED IN Misleading fault codes
Raw body: The exact bytes received, before parsing or re-serialisation, which is what must be hashed.DEFINED IN A notification you did not ask for
Raw layer: An immutable record of what a source actually sent, kept so that any later transformation can be re-derived.DEFINED IN Refinement stages
Rayleigh collapse: The inertially driven implosion of a cavity, set by the momentum of the surrounding liquid rather than by applied pressure.DEFINED IN Sonoluminescence
Rayleigh distillation: Progressive depletion of a reservoir when the fraction removed is continuously withdrawn rather than kept in contact.DEFINED IN Rainfall isotope distillation
Rayleigh distribution: The wave-height distribution implied by a narrow-banded Gaussian sea, giving an exceedance probability of exp(-2x²).DEFINED IN Rogue waves
Rayleigh number: The dimensionless ratio of buoyant driving to viscous and thermal damping in a heated layer; convection begins above a critical value.DEFINED IN Convection cells
Rayleigh scattering: The scattering of light by particles much smaller than its wavelength, far stronger for short (blue) wavelengths.DEFINED IN Why is the sky blue?
Rayleigh-Bénard convection: Convection driven by buoyancy in a fluid layer heated from below and cooled above.DEFINED IN Convection cells
Re-entry cost: What a first move back toward the other party costs the mover, including exposure to an audience and to refusal.DEFINED IN Family estrangement
Reachability analysis: Deciding, from the call graph and a set of entry points, which code could possibly execute.DEFINED IN Code that never runs, and code that runs once a year
ReAct: The 2022 formulation of interleaving reasoning steps with actions in a single loop.DEFINED IN The agent loop
Reaction quotient: The same ratio evaluated at any moment; its position relative to the constant says which way the reaction will run.DEFINED IN Ammonia synthesis
Reaction-diffusion: A self-organising system of a short-range activator and a longer-range inhibitor that generates repeating patterns.DEFINED IN Morphogen gradients
Reactive hyperaemia: The surge of blood flow above baseline that follows the release of an occlusion.DEFINED IN Forearm pump in climbing
Reactive oxygen species: Chemically aggressive oxygen compounds produced when absorbed light energy cannot be routed into photosynthesis.DEFINED IN Coral bleaching
Read-your-writes: A targeted guarantee that a client always sees at least its own most recent write, layered on top of eventual consistency.DEFINED IN Eventual consistency
Read-your-writes consistency: The guarantee that a client always sees the effect of its own earlier writes.DEFINED IN Replication lag
Readiness potential: A slow build-up of scalp-recorded brain activity preceding voluntary movement, central to Libet's experiments.DEFINED IN Free will
Reading against the grain: Extracting from a document what its author did not intend to record, including what its categories imply.DEFINED IN Historical silence
Readmission agreement: A treaty under which a state accepts the return of its own nationals, without which removal is impracticable.DEFINED IN Visa reciprocity
Real option: The right but not the obligation to take a future action, bought with a premium paid now.DEFINED IN The price of being able to leave
Real return: The growth left after inflation has been taken out; the only part that buys more than before.DEFINED IN Compound interest
Real user monitoring (RUM): Telemetry reported from actual user sessions, capturing the true distribution of devices, networks and data.DEFINED IN Synthetic versus real users
Reanalysis: A learner assigning a different structure to what they hear, as when a napronDEFINED IN Why do languages change over time?
Reaping: Reading a terminated child's exit status so the kernel can free its process table entry.DEFINED IN The first process
Reasoning model: A model trained specifically to make long private working productive rather than merely longer.DEFINED IN Thinking budget
Rebound effect: The tendency to consume some of an efficiency gain as extra comfort, so measured savings fall short of predicted ones.DEFINED IN Home insulation
Rebus principle: Using a sign for the sound of its word rather than its meaning, the step that lets writing represent speech.DEFINED IN Writing invention
Recall: The ability to return to a previously rejected option; assumed absent here.DEFINED IN Optimal stopping
Recall (sensitivity): The share of real conditions that the alert catches; raising it usually lowers precision.DEFINED IN Alert fatigue
Recall at k: The fraction of the true top-k results an approximate search actually returns, measured against brute force.DEFINED IN Approximate nearest neighbour search · Evaluating retrieval separately · Two-stage retrieval
Receipt-freeness: The property that a voting system gives the voter no evidence of how they voted.DEFINED IN Secret ballot
Recency weighting: Scoring older memories lower at retrieval so they fade without being deleted.DEFINED IN What an assistant should forget
Receptive competence: The ability to understand a language without being able to produce it fluently.DEFINED IN Heritage language loss
Recertification: A periodic review in which each grant must be re-justified or is removed.DEFINED IN Roles as compression
Recharge and discharge: The slow build-up and drainage of warm water volume in the equatorial band that supplies the cycle's delay.DEFINED IN El Nino oscillation
Reciprocal rank fusion: Combining ranked lists by summing one over a constant plus each document's rank in each list, ignoring the underlying scores.DEFINED IN Hybrid search
Reciprocity: The working assumption that halving the brightness and doubling the time produces the same damage.DEFINED IN Museum lighting
Reciprocity law: The assumption that photographic effect depends only on illuminance times time.DEFINED IN Reciprocity failure
Reciprocity mechanism: A rule committing a state to reimpose visa requirements on a country that does not extend equivalent access to all of its citizens.DEFINED IN Visa reciprocity
Reclaim: The kernel's process of freeing pages by evicting clean cache, writing back dirty pages, or swapping, before resorting to killing anything.DEFINED IN Killed with memory to spare
Reclassification: The deliberate re-assessment and relabelling of data whose sensitivity has changed.DEFINED IN Labelling before deciding
Recognition-primed decision: Klein's account in which experts recognise a situation type, generate one course of action, and simulate it rather than compare alternatives.DEFINED IN Skilled diagnosis
Recollection: Retrieval of an episode together with its context: when, where, and what surrounded it.DEFINED IN Deja vu
Reconciliation: The check that every bag in the hold corresponds to a passenger who actually boarded.DEFINED IN Baggage reconciliation · Budget scoring windows · Grade earned, not declared · Two systems, one record
Reconciliation loop: A repeating cycle that observes actual state, compares it to declared state, and applies the difference.DEFINED IN Declaring the destination, not the route
Reconsolidation: The finding that reactivating a stable memory makes it briefly modifiable before it is stored again.DEFINED IN Memory reconstruction
Reconstitution: Forming a fresh reserve immediately after the previous one is committed, often from whatever can be spared.DEFINED IN Holding a reserve
Record linkage: Deciding which records across sources refer to the same real-world entity.DEFINED IN Which record is the real one
Recovery efficiency: The fraction of applied nutrient that ends up in the harvested crop in the season of application.DEFINED IN Diminishing fertiliser returns
Recrystallisation: Growth of new strain-free grains on heating, erasing stored deformation.DEFINED IN Work hardening
Rectifiable curve: A curve whose measured length converges to a finite value as the ruler shrinks, which coastlines are not over the range measured.DEFINED IN Coastline paradox
Recurrent network: A model that reads a sequence one element at a time, carrying a hidden state forward.DEFINED IN Transformer parallelism
Recurrent walk: One that returns to its starting point with probability 1.DEFINED IN Random walk recurrence
Recursive CTE: The SQL:1999 construct letting a query refer to its own partial results, enabling tree walks.DEFINED IN A tree in a table of rows
Recusal: A judge's withdrawal from a case, on their own motion or a party's application.DEFINED IN Judicial recusal
Recycling: The spin-up of an old neutron star by accretion from a binary companion, producing a millisecond pulsar.DEFINED IN Pulsar spin rates
Red detuning: Tuning a laser below an atomic resonance, so motion towards the beam brings the light into resonance.DEFINED IN Laser cooling
Red Queen hypothesis: The proposal that sex is maintained by continual coevolution with parasites, which track common host genotypes.DEFINED IN Cost of sexual reproduction
Red-black tree: A search tree using colour rules to keep the longest path at most twice the shortest.DEFINED IN A tree that rearranges itself
Red-green-refactor: The three states of that cycle, named for the test runner's colours.DEFINED IN Writing the test first
Redlining: The 1930s US practice of grading neighbourhoods for mortgage-insurance risk, marking many minority areas as hazardous.DEFINED IN Persistent poor neighbourhoods
Redressability: The requirement that the relief sought would actually remedy the claimant's injury.DEFINED IN Standing to sue
Redshift: The stretching of light to longer wavelengths, here caused by the expansion of space during its journey.DEFINED IN Dark night sky
Redshifted 21-centimetre line: Neutral hydrogen's 1420 MHz emission, stretched by cosmic expansion into the low-frequency band.DEFINED IN Low-frequency radio cutoff
Reducing sugar: A sugar with a chemically open, reactive end, such as glucose or fructose.DEFINED IN Maillard browning
Reductionism (about testimony): The view that testimony's justification derives from the hearer's own perception, memory and inductive track record.DEFINED IN Knowledge from testimony
Redundancy effect: The finding that information duplicating what a learner already has impairs learning rather than leaving it unchanged.DEFINED IN Expertise reversal · Split attention in materials
Refactoring: Changing a program's internal structure without changing its external behaviour.DEFINED IN Technical debt
Reference class forecasting: The formal method of placing a project in a class of completed ones and forecasting from that record.DEFINED IN Planning fallacy
Reference drift: The sharpening and rising of a judge's internal standard as the session supplies real examples of the class being judged.DEFINED IN Judging order effects
Reference point: The standard of comparison, largely set by recent experience, against which a present circumstance is judged.DEFINED IN Fasting · Framing · Hedonic adaptation · Wage stickiness
Reference set: A fixed sample of the original data kept for comparison, so that today's inputs can be measured against what the model was actually fitted to.DEFINED IN Model drift
Referential novelty: Whether a thing being mentioned is new to the conversation or already established, which strongly predicts where a speaker hesitates.DEFINED IN Filler words
Referential stability: The property that a reference keeps pointing at the same entity regardless of changes to that entity's attributes.DEFINED IN Surrogate keys
Referred pain: Pain perceived at a site distant from the tissue actually damaged.DEFINED IN Referred pain
Reflection cracking: A crack in a new surfacing that propagates upward from a joint or crack in the layer beneath.DEFINED IN Road cracking
Reflector: Surrounding material that scatters escaping neutrons back inside, lowering the critical mass.DEFINED IN Critical mass
Refractive index: How strongly a material bends light, and thus how optically different it is from its neighbours.DEFINED IN Emerging pentimenti · Guided light · Night window reflections · Soap film colours
Refresh token: A longer-lived credential, used only at the authorization server, that obtains new access tokens.DEFINED IN Delegation without the password
Refresh-token rotation: Issuing a replacement refresh token on every use and retiring the presented one.DEFINED IN Detecting a theft you cannot see
Refrigerant: The working fluid that absorbs and releases heat.DEFINED IN How does a refrigerator cool food?
Regelation: The melting of ice under pressure and its refreezing when the pressure is released.DEFINED IN Slippery ice
Regenerated production: Growth supported by nutrients recycled within the lit layer.DEFINED IN Ocean productivity
Register: The variety of language appropriate to a situation: vocabulary, formality, degree of hedging, and what is left unsaid.DEFINED IN A calibrated role · Headlinese
Registered replication report: A coordinated multi-laboratory attempt at a single finding, agreed in advance and published regardless of outcome.DEFINED IN Decision fatigue
Registration: Firing observed rounds at a known point to correct for the day's conditions, historically slow and itself revealing.DEFINED IN Shoot-and-scoot artillery
Regression: A behaviour that used to be correct and no longer is; the class of damage a suite is best at catching.DEFINED IN Evaluation suites · Sibling regression
Regression discontinuity: A design that compares outcomes just either side of an arbitrary threshold, holding fixed everything that varies smoothly across it.DEFINED IN Border prosperity discontinuity · Class-size cutoff rules · Grade retention
Regression to the mean: The tendency of an extreme measurement to be followed by a more ordinary one, because part of the extreme was noise.DEFINED IN Junior champions · Placebo effect · Promotion mismatch · Regression to the mean · Sibling deidentification · Teacher expectations
Regular sound change: A shift affecting every word containing a given sound in a givenDEFINED IN Why do languages change over time?
Regularization: A penalty added to the fitting objective to discourage complexity, e.g. ridge or lasso.DEFINED IN Overfitting
Regulatory capture: The persistent tilting of a regulator's decisions toward the interests of those it regulates.DEFINED IN Regulatory capture
Rehearsal loop: The inner-voice system of working memory that keeps a short sequence alive by repeating it.DEFINED IN Earworms
Rehypothecation: A lender's re-use of collateral it has received to secure its own borrowing.DEFINED IN Overnight repo lending
Reinsurance: Insurance bought by insurers, pooling books across perils and regions that are uncorrelated with each other.DEFINED IN Insurance pooling
Rejuvenation: Erasing that history by heating above the transition and re-cooling.DEFINED IN Physical ageing of plastics
Relation R: Parfit's name for psychological connectedness and continuity with the right cause, which he argues is what matters in survival.DEFINED IN Splitting a person in two
Relationship-specific investment: An outlay whose value depends on a particular relationship continuing, and largely lost if it ends.DEFINED IN Hostage capital
Relationship-specific measurement: Assessing attachment toward one named person rather than in general; typically the better predictor of what happens with that person.DEFINED IN Adult attachment patterns
Relative age: A child's age within their competition band, as distinct from their absolute age.DEFINED IN Relative age effect
Relative deprivation: Discontent measured against an expected standard rather than an absolute one.DEFINED IN Revolution timing
Relative price: What one good trades for in terms of another, as distinct from its money price or its affordability out of income.DEFINED IN Cost disease
Relative risk reduction (RRR): The ARR expressed as a fraction of the untreated rate.DEFINED IN Number needed to treat
Relative sea level: The height of the sea surface measured against the local land, which is what a tide gauge and a coastline both experience.DEFINED IN Sea level fingerprints
Relative sea-level rise: The change in sea height as experienced at a coast, combining the ocean's rise with the land's own vertical motion.DEFINED IN Delta subsidence
Relative volatility: How much more readily one component enters the vapour than the other; an azeotrope is where it equals one.DEFINED IN Azeotropes
Relaxation: Offering a neighbour a shorter tentative distance via the node just settled.DEFINED IN Nearest first
Relaxation time: The characteristic interval over which a material's internal structure rearranges enough to shed an imposed stress.DEFINED IN Viscoelastic putty
Relaxed field: The condition of being fed, safe and unstressed, which play across species requires before it appears.DEFINED IN Children's play
Relay: The process that reads unsent outbox rows, publishes them, and marks them sent.DEFINED IN The outbox
Relay attack: Forwarding a legitimate proof to a different verifier, defeated by binding the signed material to the session and origin.DEFINED IN A secret you never send
Reliability: The consistency of scores across occasions, forms, or markers; necessary for a defensible inference but not sufficient.DEFINED IN Test validity · Value-added ranking instability
Reliability-centred maintenance: Choosing tasks from how each item actually fails and how bad the consequence is, rather than from a calendar.DEFINED IN Failure after repair
Relic: A bodily remain or object held to have been in contact with a holy person or event.DEFINED IN A relic proved false
Relict landform: A feature formed under past conditions and no longer actively developing.DEFINED IN Patterned ground
Relief theory: The account, associated with Spencer and Freud, that laughter discharges built-up nervous or social tension.DEFINED IN Explained jokes
Religious ambiguity: Hick's thesis that the world admits of a consistent interpretation both with and without God.DEFINED IN Faith and evidence
Relying party (RP): An application that trusts an identity provider to authenticate users.DEFINED IN Signing out everywhere
Remanent flux: The magnetisation an iron core retains after being de-energised, from which the next energisation starts.DEFINED IN Transformer inrush
Remembering self: The self that keeps the summary and makes the next decision from it.DEFINED IN Remembered holidays
Reminiscence bump: The excess of autobiographical memories from roughly ages ten to thirty, over and above what the normal forgetting curve predicts.DEFINED IN Reminiscence bump
Remittance: Money sent home by a migrant to their household of origin.DEFINED IN Remittances and the children left behind
Remobilisation: The dismantling of leaf and stem protein during senescence and its transport into the grain, the source of most grain nitrogen.DEFINED IN Yield and protein in wheat
Remodelling: The long final phase in which provisional collagen is degraded and replaced with stronger, cross-linked collagen.DEFINED IN Wound healing
Remodelling cycle: The ordered sequence of activation, resorption, reversal and formation at a single bone surface site.DEFINED IN Bone remodelling
Rendezvous hashing: An alternative scoring each server for a key and picking the maximum.DEFINED IN Adding a machine without moving the data
Rent: The surplus a job pays over what the same worker could earn in the next-best post, and therefore what dismissal takes away.DEFINED IN Paying above the market
Rent dissipation: The competing away of the surplus a resource could yield, through effort spent contesting it.DEFINED IN Race to fish under quota
Rent gap: The difference between what a plot currently yields under its existing use and what it could yield under its best use, which widens with disinvestment and triggers reinvestment when wide enough.DEFINED IN Gentrification
Rent-sharing: The alternative explanation that high wages reflect a firm passing on profits, rather than purchasing effort.DEFINED IN Paying above the market
Rentier state: A state funded mainly by externally-paid rents rather than domestic taxation; the term is Hossein Mahdavy's.DEFINED IN Resource revenue and accountability
Reorder point: Expected lead-time demand plus safety stock.DEFINED IN Safety stock
Repair: An exchange that resolves a grievance rather than deferring it, returning the relationship's tolerance to something like its earlier level.DEFINED IN The small last straw
Reparation: The material component of putting a wrong right, insufficient on its own for the repair of standing.DEFINED IN Apology and repair
Repeat-purchase mechanism: The argument that sellers sustain quality when the future business forfeited by cheating exceeds the immediate gain.DEFINED IN Landmark restaurants
Repeated-bout effect: The marked protection against soreness and damage conferred by a single previous bout of the same exercise.DEFINED IN Delayed muscle soreness
Repeater spacing: The distance between amplifiers, set on a submarine cable as much by the shared shore power budget as by optical loss.DEFINED IN Guided light in fibre
Repetition priming: The well-established speeding of recognition for a recently encountered word, which runs opposite to satiation.DEFINED IN Semantic satiation
Replacement selection: A run-generation technique using a heap and a watermark, producing runs about twice the size of memory on random input.DEFINED IN Sorting more than fits
Replay: Re-running a workflow from its first line while answering already-completed steps from the history rather than performing them.DEFINED IN Durable execution · Replay determinism · Sleeping on a problem
Replay attack: Re-sending a captured, genuinely valid message to cause its effect again.DEFINED IN A notification you did not ask for
Replication lag: The interval between a change committing on the primary and a given replica having applied it.DEFINED IN Replication lag
Repose: The interest in eventually being free of liability for past conduct, independent of any question about evidence.DEFINED IN Statutes of limitation
Repositioning: Moving equipment, loaded or empty, to where the next demand for it arises rather than to where cargo is going.DEFINED IN Empty container repositioning
Repository: An object that presents stored domain objects as if they were an in-memory collection, hiding the query mechanics.DEFINED IN Objects that do not know they are stored
Repurchase agreement: A sale of securities combined with an agreement to buy them back at a set price on a set date, economically a secured loan.DEFINED IN Overnight repo lending
Reputational herding: The tendency to match peers' choices because being wrong alone is penalised more heavily than being wrong together.DEFINED IN Media sameness
Request pricing: A charge per operation against a service, independent of how much data the operation moves.DEFINED IN Metered cost
Request-scoped state: Data tied to one caller and one request, which must not outlive it.DEFINED IN Warm reuse leaks
Reranker: A second-stage model that reorders retrieved candidates, offering a place to apply trust signals.DEFINED IN Planting the source it will cite
Reserve: A formed body withheld from the action, and the standard countermeasure here.DEFINED IN Feigned retreat · Holding a reserve
Reserve price: A minimum below which the seller declines to sell.DEFINED IN Auction prices
Reserves: Accounts commercial banks hold at the central bank, used to settle payments between banks.DEFINED IN Bank money creation
Reservoir age: The apparent radiocarbon age of a living organism, caused by the carbon pool it exchanges with being depleted relative to the atmosphere.DEFINED IN Marine reservoir age
Residence time: The reservoir of an element divided by its input rate: how long an average atom stays dissolved before removal.DEFINED IN Sea saltiness
Residual control rights: The authority to decide matters the contract left unspecified; in the property-rights account, this is what ownership means.DEFINED IN Boundaries of the firm
Residual leaf area: The photosynthetic surface left standing after grazing, which determines how quickly regrowth can fund itself.DEFINED IN Grazing rest period
Residual reservation: The tendency to protect land left over after other uses have been allocated, rather than land selected for its biological value.DEFINED IN Where parks end up
Residual risk: The exposure remaining after a survey, bounded only if the survey's limits are recorded.DEFINED IN Writing down what you could not determine
Residual stress: Stress remaining in a body with no external load applied, necessarily summing to zero across the section.DEFINED IN Tempered glass
Residual zone: A region where languages accumulate over long periods because no expansion displaces them.DEFINED IN Mountain language diversity
Resistance gene: DNA that helps a bacterium survive an antibiotic.DEFINED IN How does antibiotic resistance develop?
Resistive heating: Power turned to heat in a conductor, equal to current squared times resistance.DEFINED IN Coiled extension lead
Resistive loss: Power dissipated as heat in a conductor, equal to the square of the current times the resistance.DEFINED IN High-voltage transmission
Resistive touchscreen: The older design in which pressure closes a contact between two conductive layers, so any object that presses works.DEFINED IN Capacitive sensing
Resistome: The full collection of resistance genes present in an environment, including those in bacteria that have never met a clinical antibiotic.DEFINED IN How does antibiotic resistance develop?
Resolver: The function that produces the value for a single field, invoked per field per object.DEFINED IN Letting callers ask for exactly what they want
Resorption: The withdrawal of nutrients — chiefly nitrogen and phosphorus — from a leaf backDEFINED IN Why do leaves change color?
Resource: Application-controlled content, addressed by URI, that the host loads into context on its own initiative.DEFINED IN Control as a classification
Resource allocation process: The routine by which a firm ranks projects, using its current customers, margins and scale as the yardstick.DEFINED IN Incumbent disruption
Resource budget model: The account in which a tree accumulates stores over several years and depletes them in a heavy seed year.DEFINED IN Mast seeding
Resource contention: An apparent ordering caused by two jobs competing for something exclusive.DEFINED IN Recovering a schedule nobody wrote down
Resource curse: The bundled claim that resource wealth worsens growth, conflict, or governance; disputed, notably by Haber and Menaldo.DEFINED IN Resource revenue and accountability
Resource indicators (RFC 8707): A mechanism letting a client request a token restricted to a named resource server.DEFINED IN A valid token in the wrong place
Restatement: Republishing a previously final figure with corrected values, as distinct from posting a dated correcting entry in the current period.DEFINED IN Late-arriving data
Restricted three-body problem: The idealisation in which two massive bodies orbit each other circularly and a third, of negligible mass, moves in their combined field.DEFINED IN Lagrange points
Resultant luck: Luck in how one's actions turn out; the drunk drivers' case. Its siblings are circumstantial luck, in the tests one happens to face, and constitutive luck, in the unchosen temperament one brings to them.DEFINED IN Moral luck
Resurgence: The return of a target pest to densities above its pre-treatment level, following a treatment it was susceptible to.DEFINED IN Pest resurgence · Sinking streams in karst
Resuspension: Settled particles being lifted back into the air by disturbance, giving them a second chance to be ventilated out.DEFINED IN House dust
Retardation factor: Spot distance divided by solvent-front distance; equivalently the fraction of the run a molecule spent in the mobile phase.DEFINED IN Paper chromatography
Rete mirabile: Literally "wonderful net": a bundle of interwoven fine arteries and veins that maximises exchange area in a short span.DEFINED IN Countercurrent heat exchange
Retention: How far back in time recoverable copies exist, which limits recovery from damage discovered late.DEFINED IN Recovery objectives
Retention policy: The rule deciding how long a record survives, independent of whether anyone has read it.DEFINED IN Delivered versus retained
Retention schedule: A per-category statement of how long each kind of record is kept, and on what basis.DEFINED IN Data you keep is data you can lose
Retention test: A delayed test with feedback withdrawn, used because practice-session performance does not measure learning.DEFINED IN Practice feedback
Reticulocytes: Immature red blood cells, whose proportion indicates how fast the marrow is currently producing.DEFINED IN Athlete biological passport
Retrieval: Fetching the relevant text at query time so the model reads it rather than recalls it.DEFINED IN Fine-tuning versus retrieval
Retrieval poisoning: Inserting crafted documents into a corpus so they are selected and repeated as evidence.DEFINED IN Planting the source it will cite
Retrieval practice: The strengthening of memory produced by successfully pulling something back, larger when the pull is effortful.DEFINED IN Feedback timing · Learning by explaining
Retrieval strength: How accessible a memory is at this moment, given the current cues, as against storage strength, how durably it has been learned.DEFINED IN Fluency illusion
Retrieval-augmented generation: Fetching real documents and conditioning generation on them, which reduces invented references without removing unfaithful paraphrase.DEFINED IN Citation without verification · Planting the source it will cite · Retrieval-augmented generation
Retrogradation: The slow return of gelatinised starch to an ordered, crystalline arrangement on storage.DEFINED IN Bread staling
Retrograde solubility: The property of dissolving less readily as temperature rises, shown by calcium carbonate and calcium sulfate.DEFINED IN Limescale
Retronasal olfaction: Smelling volatiles that rise from the mouth into the nasal cavity while eating, the main source of flavour.DEFINED IN Inflight taste
Retrospective duration judgement: An estimate of how long an interval lasted, made after it has ended, from what remains in memory.DEFINED IN Return-trip effect
Retrospective timing: Judging a duration afterwards, from what it left in memory.DEFINED IN Sense of time
Retry budget: A cap on retries as a proportion of total traffic, so retrying stops being free when failure is widespread.DEFINED IN Retry storms
Return flow: Irrigation water that percolates or runs off back to the aquifer or river, and is available again downstream.DEFINED IN Irrigation efficiency paradox
Return-trip effect: The reliable finding that a return journey is remembered as shorter than an outward journey of equal duration.DEFINED IN Return-trip effect
Reuse detection: Treating the presentation of an already-retired token as evidence of compromise.DEFINED IN Detecting a theft you cannot see
Revenue equivalence: The result that, under independent private values and similar risk-neutral bidders, the standard formats yield the same expected revenue.DEFINED IN Auction prices
Revenue management: Forecasting demand and controlling how much inventory is released at each price over time, weighing a sale now against a better sale later.DEFINED IN Different prices, same room
Reverberation time (RT60): How long a sound takes to fall by sixty decibels in a room; the standard measure of acoustic liveness.DEFINED IN Architectural atmosphere · Concert hall reverberation
Reversal curse: Failure to answer a fact in the opposite direction from the one it was trained in.DEFINED IN Fine-tuning versus retrieval
Reverse Brazil-nut effect: The observed sinking of a large intruder under conditions where air and density ratio dominate.DEFINED IN Brazil-nut effect
Reverse camber: The bow a ski takes when pressed on edge, bringing the whole edge into contact.DEFINED IN Carving ski sidecut
Reverse causation: The outcome causing the supposed cause, here a birth prompting a grandmother's move.DEFINED IN Grandmother proximity and fertility
Reverse Magnus effect: The curve running opposite to the spin, in a narrow band where only one side's boundary layer is turbulent.DEFINED IN Magnus effect
Reverse onus: A rule placing on the accused the burden of establishing some particular matter.DEFINED IN Presumption of innocence
Reversibility: How cheaply, and whether at all, an action's effects can be undone.DEFINED IN Autonomy as a dial · Patina and age value
Revocation latency: The time between compromise and the credential ceasing to work, which forms part of the reach.DEFINED IN Blast radius · You cannot un-issue a signature
Revolutionary threshold: The number of others already participating that would make a given person join.DEFINED IN Revolution timing
Revolving door: Movement of personnel between a regulator and the industry it oversees, in both directions.DEFINED IN Regulatory capture · Term limits
Rewiring probability: In the Watts-Strogatz model, the chance that a given local edge is redirected to a random node.DEFINED IN Small-world networks
RFC 7009 token revocation: The OAuth endpoint a client calls to revoke a refresh or access token at the authorization server.DEFINED IN Signing out everywhere
RFC 7662 token introspection: The endpoint a resource server calls to ask whether a token is still active, trading a round trip for freshness.DEFINED IN Signing out everywhere
Rhizobia: Soil bacteria living in legume root nodules that convert atmospheric nitrogen into a form the plant can use.DEFINED IN Crop rotation
Rice's theorem: The result that every non-trivial property of the function a program computes is undecidable.DEFINED IN Halting problem
Richardson effect: The empirical finding that measured length rises as a power of the measuring scale for natural boundaries.DEFINED IN Coastline paradox
Ride-down: Coupling the occupant to the decelerating structure early, so they share the vehicle's whole stopping distance.DEFINED IN Crumple zones
Right to repair: Policy requiring makers to supply spare parts, tools, and documentation to owners and independent repairers.DEFINED IN Repair economics
Right-censoring: Observation of a case that ends at a known time with the event of interest still not observed.DEFINED IN Censored follow-up
Right-skewed distribution: One with a floor, a dense low region, and a long tail of large values, in which the mean exceeds the median.DEFINED IN Why the average recovery time lies
Rights amplification: Deriving a higher-privilege key from a lower-privilege one.DEFINED IN Master keying
Rinse aid: A surfactant that lowers water's surface tension so it sheets off a surface and drains rather than beading up on it.DEFINED IN Dishwasher drying
Risk class: A grouping of operations by consequence: reversible, costly, destructive, externally visible.DEFINED IN Tool granularity
Risk compensation: The tendency to spend an improvement in safety on greater performance, so the realised risk falls by less than the improvement.DEFINED IN Experienced-worker injuries
Risk pooling: Combining many risks so that the average outcome becomes predictable, even though the total exposure grows.DEFINED IN Insurance pooling
Risk premium: The part of an interest rate that covers expected losses from borrowers who do not repay.DEFINED IN Credit
Risk set: The patients still under observation and event-free immediately before a given time.DEFINED IN Censored follow-up
Risk-spreading: Reducing exposure to any single shock by distributing ties across several independent households.DEFINED IN Child fostering
Rite of passage: Van Gennep's name for a ritual moving a person between social statuses, in three phases: separation, margin, reincorporation.DEFINED IN Liminality in initiation
Ritualisation: The process by which an instrumental action becomes valued for its performance rather than its effect.DEFINED IN Ceremony as a smell
RLHF: Reinforcement learning from human feedback, one of the later stages that turns a text continuer into an assistant.DEFINED IN Next-token prediction
Roche limit: The distance inside which tidal stretching exceeds a body's own self-gravity, so loose material cannot hold together.DEFINED IN Planetary rings
RoCoF: Rate of change of frequency, the speed at which frequency moves after an imbalance; higher when inertia is low.DEFINED IN Grid balancing
Rod-cone break: The kink in the dark-adaptation curve where rods overtake cones as the more sensitive system, typically several minutes in.DEFINED IN Dark adaptation
Role (or echelon) of care: A defined level of medical capability, sited by transport time rather than by casualty numbers.DEFINED IN Casualty evacuation
Role explosion: The unchecked growth of a role catalogue toward one role per person, dissolving the benefit of grouping.DEFINED IN Roles as compression
Role prompting: Opening a prompt by assigning the system an identity or persona in order to shape its response.DEFINED IN A calibrated role
Role reversal: The exchange of dominant and subordinate positions during a play bout, rare or absent in serious contests.DEFINED IN Children's play
Role-based access control (RBAC): Granting permissions via named roles rather than assigning them to individuals directly.DEFINED IN Roles as compression
Rolling without slipping: The constraint that the contact point has zero instantaneous velocity, which links a body's rotation to the motion of its contact.DEFINED IN A spinning coin's last rattle
Root-sum-square stacking: Combining tolerances in quadrature, valid for independent, centred processes, giving the square root of n rather than n for equal terms.DEFINED IN Tolerance stack-up
RoPE: Rotary position embedding, a widely used relative position scheme whose interaction strength decays with distance.DEFINED IN Lost in the middle
Rotation: The constant-time pivot of a parent and child that changes local height while preserving in-order sequence.DEFINED IN A tree that rearranges itself · Schedule padding
Rotation curve: Orbital speed plotted against distance from a galaxy's centre.DEFINED IN Galaxy rotation curves
Rough-in (first fix): The stage at which cables, pipes and ducts are run and fixed but nothing is connected, finished or covered.DEFINED IN Rough-in inspection
Roughness: The grating quality heard when two components are too close in frequency for the ear to resolve them separately.DEFINED IN Musical consonance
Rout: The collapse of a formation into individual flight, historically the phase in which most casualties occur.DEFINED IN Feigned retreat
Route template: A normalised path such as /orders/{id} used in place of raw URLs to keep endpoint cardinality bounded.DEFINED IN Metric cardinality explosion
Router: A component that predicts, from the request, which model tier should handle it.DEFINED IN Model routing
Row group: A horizontal block of rows within a columnar file, the smallest unit statistics usually cover.DEFINED IN Partition pruning
Row store / column store: Storing a record's fields together, versus storing a column's values together.DEFINED IN Two stores for one truth
Row versioning: Storing one row per era of an entity, each with the interval in which it applied.DEFINED IN Recording a change without losing the present
RPO (recovery point objective): The maximum amount of data, expressed as a time window, that the business accepts losing in a disaster.DEFINED IN Recovery objectives
RTO (recovery time objective): The maximum acceptable time between failure and restored service.DEFINED IN Recovery objectives
RuBisCO: The enzyme that fixes carbon dioxide; slow, and prone to reacting with oxygen instead.DEFINED IN Photosynthesis
Rule consequentialism: The view that the right act is what a code would permit whose general acceptance would have the best consequences.DEFINED IN Keeping a rule against the case
Rule of 72: Divide 72 by the percentage rate for a quick estimate of the years to double; it approximates ln2/r.DEFINED IN Compound interest
Rule of three: The heuristic of waiting for a third occurrence before extracting a shared abstraction, so the axis of variation is visible.DEFINED IN When removing duplication hurts
Rule worship: Smart's charge that following a rule known to produce a worse outcome treats the rule as an end in itself.DEFINED IN Keeping a rule against the case
Rumen papillae: Absorptive projections of the rumen wall, which regress on a bulky diet and regrow over weeks on a fermentable one.DEFINED IN Dairy cow energy balance
Run: A contiguous, internally sorted stretch of records written out during the first phase.DEFINED IN Sorting more than fits
Run-up: The maximum vertical height above sea level reached by the water as it climbs the land, generally larger than the offshore amplitude.DEFINED IN Tsunami shoaling
Running order: The sequence in which competitors perform, often set by seeding or qualification rank rather than by lot.DEFINED IN Judging order effects
Runoff (instant-runoff): Lowest-placed candidates are eliminated in turn and their ballots transferred until someone has a majority.DEFINED IN Voting rules

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S wave: The slower, shear body wave, which requires rigidity and so cannot cross a liquid.DEFINED IN Seismic shadow zone
Sabine's equation: RT60 approximately equals 0.161 times room volume in cubic metres divided by total absorption in square metres of equivalent open window.DEFINED IN Concert hall reverberation
Saccade: The rapid jump between fixations, covering roughly eight characters in ordinary reading.DEFINED IN Legibility
Sacrificial protection: Coating with, or attaching, a metal that corrodes preferentially, such as zinc on steel.DEFINED IN Corrosion
Safe harbour: A bright line placed inside a standard, guaranteeing compliance to anyone who stays within it.DEFINED IN Bright-line rules
Safe publication: The guarantee that a thread seeing a reference also sees the fully constructed object behind it.DEFINED IN Immutability
Safepoint: A point in execution where a thread's references are inspectable; a pause cannot start until all threads reach one.DEFINED IN Garbage collection pauses
Safety stock: Inventory held to absorb demand uncertainty over the resupply lead time; its target rises with the forecast, which is what causes amplification.DEFINED IN Bullwhip effect · Safety stock
Safety-net effect: Deep tree roots intercepting nutrients leached below the crop's rooting depth.DEFINED IN Agroforestry overyielding
Saga: A long-running process of local steps, each with a compensating action, arranged by either style.DEFINED IN Choreography versus orchestration · Sagas
Salary schedule: A pay scale set by years of service and qualifications, uniform across schools within a district or system.DEFINED IN Teacher attrition in hard schools
Salience: How strongly an element stands out, determined by its contrast with what surrounds it rather than by its own properties.DEFINED IN Design restraint
Salinity: The mass of dissolved solids per unit mass of seawater, averaging about 35 grams per kilogram in the open ocean.DEFINED IN Sea saltiness
Salt: A unique per-record value mixed into the hash, defeating precomputed tables and cross-account reuse of a guess.DEFINED IN Deliberately slow password checks
Same-age comparison: Judging a retained pupil against the cohort she entered school with, who are now a grade ahead.DEFINED IN Grade retention
Same-grade comparison: Judging her against her current, younger classmates; the view a school sees daily.DEFINED IN Grade retention
Same-origin policy: The browser's default rule that a script may read only responses from its own origin; CORS relaxes this rather than replacing it.DEFINED IN CORS in the web
SameSite: A cookie attribute controlling whether the cookie is attached to requests originating from other sites.DEFINED IN Continuity over a protocol with no memory · Requests you did not make
Sampling review: Verifying a random subset of claims to estimate an error rate for the whole.DEFINED IN Documentation that points at its evidence
Sanctions: A host's withdrawal of resources from a partner that fails to deliver, as legumes do to non-fixing rhizobia.DEFINED IN Symbiosis
Sandbagging: Assigning or defending a grade harder than consensus, whether from local tradition or from unwillingness to downgrade.DEFINED IN Climbing grade drift · Handicapping
Satellite: A table of descriptive, time-stamped attributes for one hub or link, from one source.DEFINED IN Built never to be rebuilt
Saturated adiabatic lapse rate: The slower cooling where vapour is condensing, around 5 degrees per kilometre in warm moist air.DEFINED IN Cooling with altitude · Rain shadow
Saturating counter: A small counter that must be pushed repeatedly before it changes its prediction.DEFINED IN Branch prediction
Saturation: The state in which escapes and returns balance, so there is no net evaporation; relative humidity is the actual vapour pressure as a fraction of it.DEFINED IN Evaporative drying · Integrator windup · Nuclear binding energy · Transformer inrush
Saturation flow: The rate at which a standing queue discharges once fully moving, per lane.DEFINED IN Green wave signal timing
Saturation horizon: The depth below which the saturation state falls under one, shallower in cold water and rising as carbon accumulates.DEFINED IN Ocean acidification
Saturation line: The locked relationship between a pure fluid's temperature and its vapour pressure when liquid and vapour coexist.DEFINED IN Heat pipes
Saturation state: The ratio of dissolved calcium and carbonate to the amount the mineral can hold at equilibrium; above one, solid carbonate is stable, below one it dissolves.DEFINED IN Ocean acidification
SBAR: A fixed handover order (Situation, Background, Assessment, Recommendation) that compels the speaker to give an interpretation, not only facts.DEFINED IN Shift handover
SBOM: A software bill of materials: an inventory of the components contained in an artefact.DEFINED IN Provenance of what you deploy
Scale effect: The systematic change in a statistic caused by using more or fewer zones.DEFINED IN Modifiable areal units
Scale height: The vertical distance over which atmospheric density falls by a factor of e.DEFINED IN Orbital drag speed-up
Scale invariance: The property of being unchanged when every value is multiplied by a constant, as happens on a change of units.DEFINED IN Benford's law
Scale recalibration: A change in what a given rating number means to the respondent, which can imitate adaptation in self-reported data.DEFINED IN Hedonic adaptation
Scarcity rent: The extra value accruing to whoever controls access to a good that has become scarce.DEFINED IN Blockade and resolve
Scattering: Redirection of light at boundaries between regions of differing refractive index, destroying an image even when nothing is absorbed.DEFINED IN Glass transparency
Schema: A stored pattern that lets a learner recognise a problem type and treat many elements as one chunk.DEFINED IN Expertise reversal · Rumour sharpening · Tool calling boundary
Schema evolution: The rules governing how a schema may change over time without breaking existing readers or writers.DEFINED IN Data contracts
Schema Registry: A service that stores schema versions and rejects a registration that violates the configured compatibility setting.DEFINED IN Compatibility has a direction
Schwarzschild exponent: The power applied to time in the corrected exposure relation, below one for emulsions showing low-intensity failure.DEFINED IN Reciprocity failure
Schwarzschild radius: The horizon radius for a given non-rotating mass; about 3 km for the Sun's mass, and proportional to mass.DEFINED IN What is a black hole?
Scope: The requested and granted set of operations a token permits.DEFINED IN Delegation without the password
Score inflation: A rise in scores on one test not matched on other measures of the same domain.DEFINED IN Teaching to the test
Score reservation: Holding back the top of a bounded scale early in a session, to preserve the ability to separate better performances later.DEFINED IN Judging order effects
scratch: The empty base image, usable when a binary is statically linked and needs nothing else.DEFINED IN Building somewhere you do not ship from
Screed: The levelling layer of mortar laid over a slab, in which underfloor heating pipes are usually embedded.DEFINED IN Cold floors
Screen temperature: Air temperature measured in a ventilated shelter 1.25 to 2 metres above ground, the figure normally quoted.DEFINED IN Radiation frost
Screening: A menu offered by the uninformed party whose options are chosen differently by different hidden types.DEFINED IN Adverse selection · Anonymous giving · Costly religious demands · Credential inflation
Scribe test: A deliberate cut through a coating, after which the sideways spread of corrosion from the cut is measured.DEFINED IN Self-healing coatings
Scrubbing: Periodically reading and rewriting memory so single-bit errors are corrected before a second accumulates.DEFINED IN Radiation-hardened spacecraft computers · Silent data corruption
Sea breeze front: The leading edge of inland-moving marine air, along which air is lifted and cloud can form.DEFINED IN Sea breeze reversal
Sea control: The ability to use a given area of sea for a given period without effective enemy interference; a temporary and local condition, not ownership.DEFINED IN Fleet in being
Sea denial: Preventing an opponent from using an area, without being able to use it oneself.DEFINED IN Fleet in being
Sea level fingerprint: The distinctive geographic pattern of sea-level change produced by mass loss from one particular ice or water reservoir.DEFINED IN Sea level fingerprints
Sea lines of communication: The routes along which maritime trade and military supply actually travel, as distinct from the sea's total area.DEFINED IN Maritime chokepoints
Seal depth: The vertical height of water held in that bend, and the margin available before pressure or evaporation empties it.DEFINED IN Dry drain trap
Seal of confession: The Catholic rule that a confessor may never disclose what is heard in sacramental confession, for any reason.DEFINED IN Guaranteed secrecy
Seam: A place in an existing system where behaviour can be intercepted without changing what surrounds it.DEFINED IN Choosing the first piece to replace · Replacing a system you cannot turn off · Testability as a design property
Seasonal lag: The delay between peak sunlight and peak temperature, caused by how long land and ocean take to warm.DEFINED IN Seasons
Seat block: A quantity of seats on a scheduled or chartered service contracted in advance by a tour operator.DEFINED IN Package tour pricing
Seccomp: A filter restricting which system calls a process may make.DEFINED IN Isolation without a machine
Second collision: The occupant striking the interior after the vehicle itself has stopped; the injury mechanism restraints are designed against.DEFINED IN Crumple zones
Second serfdom: The tightening of labour dues and peasant tenure in Eastern Europe from roughly the sixteenth century, opposite in direction to the Western trend.DEFINED IN Post-plague wages · Second serfdom
Second strike: A retaliatory capability that survives a first attack, and whose survival is what makes deterrence credible.DEFINED IN Delegated launch authority
Second-degree price discrimination: Charging different amounts by letting buyers sort themselves between versions, rather than by identifying them directly.DEFINED IN Unit-price inversion
Second-harmonic restraint: Protection logic that recognises inrush by the distortion of its waveform and declines to trip.DEFINED IN Transformer inrush
Second-order bound waves: The non-sinusoidal correction that sharpens crests and flattens troughs without transferring energy between components.DEFINED IN Rogue waves
Second-strike capability: Retaliatory forces that would survive an opponent's first attack, so that retaliation remains available.DEFINED IN Deterrence
Secondary dormancy: Dormancy induced in an already-germinable seed by conditions such as burial in dark, cool, low-oxygen soil.DEFINED IN Weed seed banks
Secondary hyperalgesia: Heightened pain sensitivity in undamaged tissue surrounding an injury, the standard human evidence for a central mechanism.DEFINED IN Central sensitization
Secondary market: The resale market for works already sold once, which is where auction price series come from.DEFINED IN Death and art prices
Secondary pest outbreak: A species previously held below damaging levels by natural enemies erupting after those enemies are removed.DEFINED IN Pest resurgence
Secretary problem: The classical name for this setup: n candidates, random order, relative ranks only, irrevocable decisions, payoff only for the best.DEFINED IN Optimal stopping
Secular resonance: A slower resonance between the precession rates of orbits rather than between orbital periods themselves.DEFINED IN Kirkwood gaps
Secure base: A caregiver whose reliable availability lets a child range further and handle novelty better than they would alone.DEFINED IN Attachment · Worst behaviour at home
Security dilemma: The condition in which measures one state takes for its own security reduce the security of others, prompting responses that leave everyone less safe.DEFINED IN Security dilemma
Sediment budget: The accounting of gains and losses for a stretch of coast, whose balance sets whether it widens or retreats.DEFINED IN Downdrift beach loss
Sediment cell: A length of coast within which sediment circulates largely independently of neighbouring lengths.DEFINED IN Downdrift beach loss
Seed: The starting internal state from which a generator's entire sequence follows.DEFINED IN Pseudorandomness
Seed and soil hypothesis: Paget's proposal that organ preference reflects compatibility between tumour cell and host tissue, not circulation alone.DEFINED IN Metastasis
Seed bank: The reservoir of viable, ungerminated seeds held in the soil.DEFINED IN Weed seed banks
Seed predator: An animal that eats the seed itself, destroying it rather than moving it, as against a frugivore whose seeds survive the encounter.DEFINED IN Sweet fruit, guarded seed
Seed shadow: The spatial distribution of seed around a parent, typically peaking at the trunk and thinning steeply with distance.DEFINED IN Janzen-Connell seedling mortality
Seed vigour: The capacity of a lot to establish rapidly and uniformly across the range of conditions it may meet in the field.DEFINED IN Seed vigour versus germination
Seeding: Arranging the draw so that the strongest entrants cannot meet until late rounds.DEFINED IN Knockout upsets
Seeing: The long-exposure angular width of a stellar image, roughly λ/r₀.DEFINED IN Atmospheric seeing limit · Sky-background limit
Segregation: The separation of a plant's two gene copies into different gametes, producing Mendel's ratios in the next generation.DEFINED IN Hybrid seed decline
Segregation ice: Thin lenses formed where water is drawn to a freezing front by cryosuction, the mechanism of ordinary frost heave.DEFINED IN Pingo growth
Segregation of duties: Deliberately separating the authority to decide from the ability to execute, so neither alone can act unchecked.DEFINED IN Three kinds of responsible person
Seismic wave: Energy traveling through Earth after a sudden disturbance.DEFINED IN Why do earthquakes happen?
Selection bias: Here, the distortion from studying only artists whose work resells often enough to generate data.DEFINED IN Death and art prices · Error cancellation in averages · Random audits · Remittances and the children left behind
Selection effect: A systematic difference between what a survey can detect and what actually exists, correctable when the sensitivity is well characterised.DEFINED IN Exoplanet detection
Selection on an extreme: Choosing cases by their value on one measurement, which is what triggers the effect.DEFINED IN Regression to the mean
Selection on the dependent variable: Choosing cases by their outcome, which severs the link between the sample and the population.DEFINED IN Survivorship bias
Selection on the estimate: Promoting the intervention with the highest measured effect, which selects partly on chance and guarantees regression on retest.DEFINED IN Pilot-to-scale failure
Selection pressure: An environmental condition that changes reproductive success.DEFINED IN How does antibiotic resistance develop?
Selective assembly: Sorting parts into size bins and pairing high with low so the accumulated error cancels by construction.DEFINED IN Tolerance stack-up
Selective toxicity: Harming a pathogen far more than its host; the actual object of drug discovery.DEFINED IN Antiviral difficulty
Selectivity: The degree to which a catalyst accelerates one competing reaction more than others.DEFINED IN Catalysis · Query plan estimation
Self-attention: Each position computing a weighted combination of all positions, in a single parallel step.DEFINED IN Transformer parallelism
Self-capacitance: Sensing each electrode's capacitance to ground; simpler, but ambiguous with more than one finger.DEFINED IN Capacitive sensing
Self-consistency: Sampling several reasoning chains for one question and returning the most frequent final answer, introduced by Wang and colleagues in 2022.DEFINED IN Self-consistency · Temperature
Self-contained token: A credential carrying its own claims and signature, verifiable without consulting the issuer.DEFINED IN You cannot un-issue a signature
Self-containment: The share of a region's interactions, typically journeys to work, that begin and end inside it.DEFINED IN Functional versus administrative regions
Self-defining memory: A memory that supports a person's account of who they are, and is therefore rehearsed far more than an ordinary one.DEFINED IN Reminiscence bump
Self-describing interface: An interface that ships its own machine-readable description, so a caller can learn to use it without out-of-band documentation.DEFINED IN A schema read by two audiences
Self-expansion: Aron's model in which relationships are rewarding partly by extending the self, and which predicts that novel shared activity restores what familiarity depletes.DEFINED IN Fading attraction
Self-explanation effect: The finding that learners who explain material to themselves while studying it understand more than those who study it silently.DEFINED IN Learning by explaining
Self-fulfilling prophecy: A belief that causes the behaviour which makes it true, as distinct from a belief that merely predicts accurately.DEFINED IN Teacher expectations
Self-handicapping: A stronger play partner deliberately restraining its force or ceding advantage, keeping a weaker partner in the game.DEFINED IN Children's play
Self-heating: Temperature rise driven by an organism's own metabolism when heat generation outpaces heat loss.DEFINED IN Grain bin hot spots
Self-locking: The property of a machine so lossy that it cannot be driven backwards by its own load.DEFINED IN Mechanical advantage
Self-perception theory: The rival account holding that people infer their attitudes from their own behaviour, without any inner tension.DEFINED IN Cognitive dissonance
Self-pruning: The shedding of lower branches whose photosynthesis no longer covers their own respiration.DEFINED IN Forest height race
Self-sealing waste valve: A membrane device fitted in place of a water trap, intended for fixtures used too rarely to keep a seal.DEFINED IN Dry drain trap
Self-serve data platform: Shared infrastructure that makes publishing a good dataset cheap enough that domain teams actually do it.DEFINED IN Federated data ownership
Self-serving bias: Attributing one's successes internally and one's failures externally.DEFINED IN Attribution asymmetry
Self-stability: The ability of a riderless bicycle to recover from a disturbance without any control input, present only within a band of speeds.DEFINED IN Bicycle stability
Self-supervised pretraining: Learning from raw data by predicting part of it from the rest, needing no human labels.DEFINED IN Foundation model economics
Selfridge-Conway protocol: The first finite envy-free procedure for three participants.DEFINED IN Envy-free division
Semantic conflict: Two changes that merge cleanly as text but are logically incompatible, so the merged result is broken.DEFINED IN Merge conflicts · Merging often
Semantic differential: The rating-scale technique used to measure the strength of a word's meaning.DEFINED IN Semantic satiation
Semantic drift: A field keeping its name and type while its meaning changes, which schema checks cannot detect.DEFINED IN Data contracts
Semantic layer: A layer between physical tables and analytics tools where business definitions are declared, versioned and served.DEFINED IN The semantic layer
Semantic satiation: The temporary loss of a word's meaning under rapid repetition, recovering within seconds to minutes.DEFINED IN Semantic satiation
Semantic shift: A change in a word's meaning.DEFINED IN Why do languages change over time?
Semantic versioning: A version numbering scheme in which a major increment signals an incompatible change.DEFINED IN Backward compatibility · Dependency conflicts
Semi-additive measure: A fact summable across some dimensions but not others, such as a balance across time.DEFINED IN What one row stands for
Semi-automated offside: Limb-tracking systems that raise frame rate and automate the plane, reducing but not eliminating the choices inside the procedure.DEFINED IN Video review boundaries
Semi-decidable: A question for which an algorithm confirms every "yes" eventually but may run forever on a "no"; halting is of this kind.DEFINED IN Halting problem
Semi-major axis: The size measure of an orbit, which alone determines its period.DEFINED IN Orbital rendezvous
Semi-major axis drift: The slow secular change in orbit size produced by any persistent along-track force.DEFINED IN Yarkovsky effect
Semi-synchronous replication: Waiting for at least one replica to acknowledge before confirming the write, bounding loss without depending on all.DEFINED IN Replication lag
Semicircular canals: Three fluid-filled loops per ear that signal angular acceleration of the head.DEFINED IN Motion sickness
Senescence: The age-related decline in physiological function and rise in mortality risk, as distinct from simply getting older.DEFINED IN Senescence · Why do leaves change color?
Sense of agency: The experience that an action was performed by you, commonly modelled as a match between predicted and actual sensory outcome.DEFINED IN Self-tickling
Sensible heat: Energy transfer that raises temperature, as opposed to latent heat, which changes water's phase instead.DEFINED IN Urban heat islands
Sensitisation: The silent first phase in which IgE against an allergen is made and loaded.DEFINED IN Allergy
Sensitive dependence on initial conditions: The property that arbitrarily small differences in starting state grow into large differences in outcome.DEFINED IN Forecast horizon
Sensitivity: Of those who have the condition, the fraction the test correctly flags.DEFINED IN Screening false positives
Sensitization: An increase in responsiveness produced by a strong or noxious stimulus, which can generalize beyond the stimulus that caused it.DEFINED IN Habituation versus sensitization
Sensory attenuation: The reduced neural and perceived response to a sensation you produced yourself.DEFINED IN Self-tickling
Sensory conflict theory: The account attributing sickness to disagreement between motion signals; descriptive rather than mechanistic about the nausea itself.DEFINED IN Motion sickness
Separation load: The external load at which clamp force reaches zero and the faces part; past it the bolt carries everything.DEFINED IN Bolt preload
Separation of powers: Allocation of government functions among distinct institutions.DEFINED IN Why do democracies separate powers?
Separation of storage and compute: An architecture where data sits in cheap durable storage and processing capacity is provisioned independently.DEFINED IN Where the transform sits
Sepsis: Life-threatening organ dysfunction caused by a dysregulated host response to infection, as defined by the 2016 consensus.DEFINED IN Sepsis
Sequential depth: The number of operations that must happen strictly one after another, as distinct from total work.DEFINED IN Transformer parallelism
Serial computation: Work that must happen in order, which a fixed-depth network can only extend by emitting and re-reading tokens.DEFINED IN Chain-of-thought
Serial independence: The absence of exploitable pattern across a player's successive choices, a further prediction of equilibrium mixing.DEFINED IN Penalty aiming
Serial reproduction: An experimental chain in which each participant reproduces a message from memory for the next, with no feedback or repetition.DEFINED IN Rumour sharpening
Serializability: The guarantee that concurrent transactions produce the same result as some serial order.DEFINED IN Isolation levels
Service level indicator: A quantitative measure of some aspect of the service, usually a ratio of good events to valid events over a window.DEFINED IN Choosing an indicator
Service level objective: A target value or range for an indicator over a stated period.DEFINED IN Choosing an indicator
Service locator: A registry that classes consult at run time to obtain dependencies, keeping those dependencies out of their signatures.DEFINED IN The singleton regret
Service mesh: Infrastructure that handles service-to-service communication concerns outside application code.DEFINED IN Moving failure handling out of the program
Serviceability limit state: A design requirement about usability and comfort rather than safety, such as sway acceleration or cladding movement.DEFINED IN Building sway
Session fixation: An attack in which the attacker sets or predicts a victim's session identifier before login and relies on the application not changing it afterwards.DEFINED IN Logged into someone else's account
Session hijacking: Obtaining a victim's existing session identifier after it has been issued.DEFINED IN Logged into someone else's account
Session regeneration: Issuing a new identifier and invalidating the old one whenever the session's privilege level changes.DEFINED IN Logged into someone else's account
Set point: The target temperature the body's controls actively maintain.DEFINED IN Fever · Hedonic adaptation
Set-Cookie / Cookie: The response and request headers by which a server stores a value in the browser and the browser returns it on subsequent matching requests.DEFINED IN Continuity over a protocol with no memory
Setpoint: The value the loop is asked to hold; the only target the controller is given.DEFINED IN Feedback control
Setting block: A resilient pad carrying a pane's weight at a chosen position on the sill.DEFINED IN Setting blocks
Settled node: One whose distance Dijkstra has declared final and will not revisit; the assumption that fails under negative weights.DEFINED IN Negative edge weights
Settlement: AMQP 1.0's term for the moment a party declares it will take no further action on a delivery.DEFINED IN When responsibility transfers
Settling velocity: The steady speed at which a particle falls in still air, proportional to the square of its diameter for small particles.DEFINED IN House dust
Shade avoidance response: Stem elongation and reduced branching triggered by a low red to far-red light ratio signalling neighbours.DEFINED IN Forest height race
Shadow exchange rate: The rate the currency would trade at if the peg were dropped at this instant.DEFINED IN Currency peg collapse
Shadow infrastructure: Systems built outside the supported route, unknown to the teams responsible for them.DEFINED IN The paved road
Shadow traffic: Production requests copied to a system whose responses are discarded.DEFINED IN Running both and comparing
Shadowgraph imaging: A photographic technique that renders density changes in air visible, used to capture the whip's shock wave.DEFINED IN Whip crack
Shallow level: An impurity state lying only a few hundredths of an electronvolt from a band edge, and therefore ionised at room temperature.DEFINED IN Semiconductor doping
Shallow-water blackout: Loss of consciousness during a breath-hold from oxygen depletion before the CO2-driven urge forces a breath.DEFINED IN Breathing urge
Shallow-water wave: A wave whose length greatly exceeds the water depth, so it moves the whole column and travels at the square root of gravity times depth.DEFINED IN Tsunami shoaling
Shape from shading: The visual system's inference of three-dimensional form from graded changes in brightness across a surface.DEFINED IN Stage lighting angle
Shapiro-Stiglitz model: The 1984 account in which firms pay above market to deter shirking, and equilibrium unemployment is what makes the threat of dismissal bite.DEFINED IN Paying above the market
Shard: One of several machines or databases holding a disjoint subset of a dataset's rows.DEFINED IN Sharding
Shard key: The column whose value determines a row's shard.DEFINED IN Sharding
Shared environment: Influences that make people raised in the same family alike; small for adult personality, larger for other outcomes.DEFINED IN Sibling differences
Shattering: The wild cereal's habit of breaking its ear apart at ripeness to disperse seed; its loss is the defining crop trait.DEFINED IN Domestication
Shear line: The boundary between plug and shell, which every pin stack must clear for the plug to turn.DEFINED IN Master keying
Sheepskin effect: The earnings premium attached to completing a qualification, over and above the premium for the years of study themselves.DEFINED IN Credential inflation · Unused curriculum
Shell theorem: Newton's result that a spherical shell of matter exerts no net gravitational force on anything inside it.DEFINED IN Galaxy rotation curves
Shepherd moon: A small moon whose gravity confines a ring's edge or holds a gap open.DEFINED IN Planetary rings
Ship counter: A setting that makes a mine ignore a chosen number of passes before arming, defeating verification by transit.DEFINED IN Mine warfare
Shock front: An abrupt pressure step that forms when a disturbance outruns the speed at which the medium can respond smoothly.DEFINED IN Whip crack
Shoulder season: The weeks flanking the peak, where demand is high but no longer above capacity.DEFINED IN Shoulder-season price cliff
Shrouded attribute: A real cost not salient at the moment of choice, so competition does not compete it away.DEFINED IN Aftermarket pricing
Shuffle sharding: Giving each tenant a random subset of workers so any two overlap only partially.DEFINED IN The noisy neighbour
Side channel: An attack that infers data from observable effects such as timing, rather than reading it directly.DEFINED IN Isolates, containers, and startup cost
Side output: A separate stream to which events too late for their window are routed instead of being dropped silently.DEFINED IN Event time versus arrival time
Side-effect isolation: Confining every interaction with the outside world to separately recorded steps, so the orchestrating code stays deterministic.DEFINED IN Replay determinism
Sidecar: A proxy container deployed alongside each application instance, intercepting its network traffic.DEFINED IN Moving failure handling out of the program
Sidecut radius: The radius of the shallow arc a ski's edge forms seen from above.DEFINED IN Carving ski sidecut
Sift up / sift down: The single-path repair walks that restore the heap property after an insert or a removal.DEFINED IN Half-sorted is enough
SIGKILL: The unconditional termination signal, which no process can catch or ignore.DEFINED IN The first process
Signal: An observable feature whose value comes from what it reliably indicates about the sender, and which loses that value when anyone can display it.DEFINED IN Fashion churn · Grade inflation
Signal detection theory: A framework separating a detector's sensitivity from its decision criterion, and treating misses and false alarms as distinct costs.DEFINED IN Pareidolia
Signal erosion: The loss of informational value in a credential as it becomes more widely and uniformly awarded.DEFINED IN Grade inflation
Signal-to-noise problem: The difficulty that warning indicators are indistinguishable, in advance, from the far larger volume of irrelevant reports.DEFINED IN Fog of war · Unusable intelligence
Signalled waking: An arousal the infant announces, as distinct from the arousals every sleeper has unremarked.DEFINED IN Infant night waking
Signalling: A costly action by the informed party that only the genuinely high type would find worth taking.DEFINED IN Adverse selection · Anonymous giving · Unused curriculum
Significand: The digits of a floating-point number, separate from its exponent; a double carries 53 bits of them.DEFINED IN Floating-point error
Significant wave height: The mean height of the highest third of the waves in a record, roughly four times the standard deviation of the surface elevation.DEFINED IN Rogue waves
SIGTERM: The polite termination request, catchable so a program can shut down cleanly.DEFINED IN The first process
Silencing: McDowell's claim that in the virtuous agent a competing consideration does not register as a reason at all.DEFINED IN Effortless virtue
Silent data corruption: Data returned successfully but differing from what was written, with no error reported anywhere.DEFINED IN Silent data corruption
Silicate weathering: The acid attack on carbon-free rock that nets a permanent removal of carbon dioxide from the air.DEFINED IN Silicate weathering thermostat
Sill: The lowest point on a closed basin's rim, where a rising lake would first spill out.DEFINED IN Endorheic basins
Similarity threshold: The score above which a stored answer is considered reusable; the dial between missed reuse and wrong reuse.DEFINED IN Caching an answer nobody asked for exactly
Simmer: In strict usage, a pan held just below boiling; the distinction matters, because a true sub-boiling simmer really is slower.DEFINED IN Rolling boil versus simmer
Simple request: Roughly a GET, HEAD, or form-style POST with no unusual headers; these skip the preflight.DEFINED IN CORS in the web
Single source of truth: The property that a named quantity has exactly one authoritative definition, not merely one storage location.DEFINED IN The semantic layer
Single sourcing: Buying a part from exactly one supplier, usually for coordination and volume pricing.DEFINED IN Just-in-time fragility
Single till: A regulatory method in which commercial income is offset against the charges an airport may levy on airlines; the dual till keeps the two separate.DEFINED IN Airport layout
Single-direction folding: Folding a long strip repeatedly along the same axis, the method used for the twelve-fold result.DEFINED IN Paper folding limit
Single-elimination knockout: A format in which one defeat removes an entrant, so winning requires consecutive victories.DEFINED IN Knockout upsets
Single-event latchup: A strike that triggers a parasitic conducting path, destructive unless power is cycled quickly.DEFINED IN Radiation-hardened spacecraft computers
Single-event upset: A transient bit flip caused by one particle, correctable by rewriting.DEFINED IN Radiation-hardened spacecraft computers
Single-peaked preferences: Rankings declining in both directions from one ideal point on a shared dimension.DEFINED IN Cyclic majorities
Singleton: The pattern that ensures a class has exactly one instance and provides a global point of access to it.DEFINED IN The singleton regret
Sink: Any place a string is interpreted: a renderer, a query, a shell, a file path, a tool call.DEFINED IN Output as untrusted input
Sink capacity: The crop's own limit on where assimilate can be deposited, largely fixed by the number of grain sites set earlier in the season.DEFINED IN Diminishing fertiliser returns
Site and situation: A place's local physical character, versus its position relative to everywhere else.DEFINED IN City location
Situation model: The mental representation of what a text is about, built from the words plus the reader's knowledge.DEFINED IN Knowledge and comprehension
Situational attribution: Explaining behaviour by the circumstances the person was acting within.DEFINED IN Attribution asymmetry
Situational awareness: An operator's live model of what is happening, what it means, and what is about to happen next.DEFINED IN Shift handover
Size class: A rounded allocation size served from a dedicated pool so freed blocks are interchangeable.DEFINED IN Memory fragmentation
Size-biased sampling: Drawing items with probability proportional to their size, rather than uniformly.DEFINED IN Inspection paradox
Size-distance invariance: The rule that perceived size follows from angular size together with perceived distance.DEFINED IN Moon illusion
Size-distance paradox: The finding that observers call the horizon Moon both larger and nearer, which the apparent-distance account cannot take at face value.DEFINED IN Moon illusion
Skin depth: The depth to which an oscillating field penetrates a conductor before falling away, decreasing with frequency and conductivity.DEFINED IN Faraday cage
Sky background: Diffuse light in the aperture from airglow, scattered moonlight, zodiacal dust and unresolved sources.DEFINED IN Sky-background limit
Sky view factor: The fraction of sky visible from a point; low in a narrow street, which slows night-time radiative cooling.DEFINED IN Urban heat islands
Sky-limited regime: The condition where background shot noise dominates read noise and source noise, so depth grows as the square root of time.DEFINED IN Sky-background limit
Skywave: A signal refracted back to earth by the ionosphere, allowing propagation far beyond the horizon.DEFINED IN Radio diffraction
Slack: Scheduled connection time minus that minimum; the only part a delay can consume without consequence.DEFINED IN Missed connections
Sleep cycle: The repeating progression through sleep stages, ending in a brief arousal, shorter in infants than in adults.DEFINED IN Infant night waking
Sleep inertia: The transient impairment of alertness and performance immediately after waking, worst when the sleeper is woken from slow-wave sleep.DEFINED IN Nap length
Sleep pressure: The accumulating drive to sleep that builds across waking hours and is discharged by sleeping; a longer nap discharges more of it.DEFINED IN Nap length
Slendro: A five-tone system, often called roughly equidistant, with no fixed interval sizes across sets.DEFINED IN Gamelan tuning
Slot: Permission to use the runway, stand and terminal capacity of a coordinated airport at a specified time, allocated for a season.DEFINED IN Airport slot grandfathering
Slow component: The gradual rise in oxygen cost of a fixed workload during exercise above the sustainable ceiling.DEFINED IN Even pacing
Slow-wave sleep: The deepest stage of non-REM sleep, marked by large synchronised cortical waves; also called N3 or deep sleep.DEFINED IN Nap length · Sleep · Sleeping on a problem
Slowly changing dimension: A reference table that records validity intervals so an attribute can be resolved as it stood at a past date.DEFINED IN Backfilling a pipeline · Recording a change without losing the present · The untidy shape that answers faster
Slowly changing dimension (type 2): Preserving history by versioning a dimension row when an attribute changes, so old facts still point at old values.DEFINED IN Rapidly changing attributes
SLSA: A published framework of graded requirements for build integrity and provenance.DEFINED IN Provenance of what you deploy
Sludge: Friction deliberately added to a process to discourage people from completing it, the mirror image of a nudge.DEFINED IN Subscription inertia
Snapshot: A consistent one-time read of current rows, needed because a log holds changes rather than contents.DEFINED IN Change data capture · Opaque cursors · Transactions on immutable storage
Snapshot isolation: Each transaction reads a consistent frozen view; prevents most anomalies but allows write skew.DEFINED IN Isolation levels
Snapshot restore: Resuming from a memory image captured after initialisation, rather than re-running it.DEFINED IN Cold starts
Snowflake schema: A star whose dimension hierarchies are normalised into further tables, adding join depth.DEFINED IN The untidy shape that answers faster
Snowflake server: A long-lived host whose accumulated hand changes make it unique and effectively impossible to reproduce.DEFINED IN Configuration drift
Social compensation: Working harder in a group than alone, when the outcome matters and co-workers are expected to underperform.DEFINED IN Social loafing
Social jetlag: The recurring mismatch between a person's biological timing and their imposed schedule, and the weekly swing it produces.DEFINED IN Teenage sleep phase
Social loafing: The reduction in individual effort that follows from believing effort is pooled, distinct from any loss of coordination.DEFINED IN Group projects
Social proof: The tendency to infer the right choice from the choices of others under uncertainty.DEFINED IN Seating by the window
Social referencing: An infant's deliberate check of a caregiver's face to resolve an ambiguous situation, as at the visual cliff.DEFINED IN Attachment
Social-domain theory: Smetana's account that people sort issues into moral, conventional and personal domains, and that families agree about the first while disputing the boundary of the third.DEFINED IN Adolescent-parent conflict
Socioemotional selectivity theory: Carstensen's account that perceived remaining time shifts social goals from acquiring information to obtaining emotional meaning.DEFINED IN Shrinking social circles
Sociopolitical complexity: The number of distinct roles, specialisms, and layers of control a society maintains.DEFINED IN Societal collapse
Sodicity: A high proportion of sodium among a soil's exchangeable cations, which disperses clay and destroys soil structure.DEFINED IN Salinization
Sodium D lines: The pair of sodium emission lines at 589.0 and 589.6 nanometres responsible for the familiar yellow.DEFINED IN Flame emission colours
Softmax: The normalisation that turns raw scores into positive weights summing to one.DEFINED IN Attention as a budget · Temperature
Software rejuvenation: Deliberately restarting a component before degradation causes failure, to convert unplanned downtime into planned downtime.DEFINED IN Software aging
Soil horizon: A distinct layer in a soil profile, produced as water moves material downward over long periods.DEFINED IN Soil formation
Soil water repellency: The state in which hydrophobic organic coatings on dried particles make soil resist wetting.DEFINED IN Runoff from dry ground
Sola scriptura: The Reformation principle that scripture alone is the final authority, without an interpreting magisterium.DEFINED IN Living interpretation of a fixed text
Solar absorptivity: The fraction of incident sunlight a surface takes in; coatings are chosen for a low value alongside a high emissivity.DEFINED IN Spacecraft cooling
Solar altitude: The Sun's angle above the horizon; energy delivered per unit of level ground scales with its sine.DEFINED IN Seasons
Solar noon: The moment the sun crosses the local meridian, which varies continuously with longitude.DEFINED IN Time zones
Solar wind: The continuous stream of charged particles and embedded magnetic field flowing outward from the Sun.DEFINED IN Comet tails
Solid electrolyte interphase (SEI): The passivating film on the anode, which both protects theDEFINED IN Battery ageing
Solid solution: An alloy in which the added element sits within the host lattice, either substituting for host atoms or wedged between them.DEFINED IN Alloy strength
Solidity: The fraction of the swept disc occupied by blade, high in slow windpumps and low in fast turbines.DEFINED IN Three-bladed turbines
Solubility product: The constant governing how much of a sparingly soluble compound can remain dissolved; the reason pH shifts metal availability by orders of magnitude.DEFINED IN Lime-induced nutrient lockup
Solute rejection: A growing crystal excluding dissolved material, concentrating it in the liquid just ahead of the front.DEFINED IN Cloudy ice cubes
Solvable problem: A conflict about a specific situation that a workable arrangement genuinely settles.DEFINED IN Proxy arguments
Solvency capital: Reserves held against the bad tail rather than the average, sized by regulation to a stated survival probability.DEFINED IN Insurance pooling
Somatic hypermutation: The targeted, high-rate point mutation of antibody variable-region genes in activated B cells.DEFINED IN Antibody affinity maturation
Somatosensory map: The ordered representation of body regions in sensory cortex.DEFINED IN Phantom limb pain
Sonic boom: The sound of a shock front produced by an object moving faster than sound through air.DEFINED IN Whip crack
Soot: Fine solid carbon particles formed in the fuel-rich part of the flame, which glow and are mostly consumed before escaping.DEFINED IN Candle wick
Sorites paradox: The argument that repeated tiny changes, each individually harmless, take you from a clear case to a clear non-case.DEFINED IN Vagueness
Sortal: The kind-term that fixes what is being counted, as in "same ship" versus "same collection of planks".DEFINED IN Identity over change
Sorting: The process by which households distribute themselves across a city according to what they can pay for local quality.DEFINED IN Windward wealth divide
Sound change: A systematic change in pronunciation over time.DEFINED IN Why do languages change over time?
Sound speed profile: Sound speed as a function of depth; its shape, not the water's composition, decides how sound propagates.DEFINED IN Deep sound channel
Sound-ranging: Locating a gun by timing the arrival of its report at microphones spread along a known baseline.DEFINED IN Shoot-and-scoot artillery
Soundness: Validity combined with actually true premises.DEFINED IN What makes an argument logically valid?
Source and target domain: The domain lent (usually concrete and directly experienced) and the domain borrowing it (usually abstract).DEFINED IN Metaphor
Source control: Removing or draining the physical focus of an infection, so the drug has far less to accomplish.DEFINED IN Antibiotic course length
Source monitoring: Judging where remembered content came from; its failure is what makes told details feel seen.DEFINED IN Memory reconstruction
Source of truth: The single system that accepts new facts; every other copy is derived from it.DEFINED IN Two stores for one truth
Source protection: Withholding or disguising action on intelligence so that the enemy does not learn how the information was obtained.DEFINED IN Unusable intelligence
Source-filter model: The standard account of speech as a sound source, the folds, shaped by a filter, the vocal tract.DEFINED IN Helium voice
Sourdough starter: A maintained culture of wild yeasts and lactic acid bacteria that leavens and acidifies dough.DEFINED IN What makes bread rise?
Space syntax: A research approach measuring street-network connectivity and its relation to movement; influential and contested.DEFINED IN Unplanned settlement form
Span: One unit of work, carrying a span ID, a parent span ID, a start time, a duration, and attributes.DEFINED IN Distributed tracing
Spatial coherence: Correlation of phase across the width of a beam; what makes a beam directional.DEFINED IN Laser coherence
Spatial contiguity principle: Mayer's design rule that corresponding words and pictures be placed near each other on the page or screen.DEFINED IN Split attention in materials
Spatial locality: The tendency to use data near data recently used; what makes contiguous layouts fast.DEFINED IN Fewer operations, slower program
Spawn: A carrier such as grain or sawdust already fully colonised by the mushroom, used as the inoculum.DEFINED IN Pasteurised mushroom substrate
Spearman-Brown formula: The relation giving the reliability of an averaged measurement from the reliability of a single one and the number averaged.DEFINED IN Marker disagreement
Specific heat capacity: The energy needed to raise one kilogram of a substance by one kelvin.DEFINED IN Rolling boil versus simmer · Sea breeze reversal
Specific orbital energy: Total energy per unit mass of an orbit, negative for any bound orbit and equal to -GM/2a.DEFINED IN Orbital drag speed-up
Specificity: Of those who do not have it, the fraction the test correctly clears.DEFINED IN Screening false positives
Speckle: One of the many λ/D-sized grains a short exposure resolves the blur into.DEFINED IN Atmospheric seeing limit
Spectral class: The O-B-A-F-G-K-M ordering by absorption lines, hottest to coolest.DEFINED IN Star colors
Spectral evidence: Testimony that the accused's apparition afflicted a victim, visible only to the afflicted, and repudiated at Salem.DEFINED IN Witch-hunt cascades
Speculative attack: The concentrated sale of a pegged currency to the central bank at the pegged price, once that price favours the seller.DEFINED IN Currency peg collapse
Speech surrogate: Any system that re-encodes a spoken language in another medium rather than replacing it with a separate code.DEFINED IN Whistled languages
Speleothem: Any secondary mineral deposit formed inside a cave, such as a stalactite or stalagmite.DEFINED IN Cave formation
Spending power: The authority to attach conditions to money disbursed, distinct from authority to regulate the subject of those conditions.DEFINED IN Conditional spending grants
Spike: A short exploratory piece of code written to learn something, usually thrown away, and normally exempt from test-first discipline.DEFINED IN Writing the test first
Spin ratio: Surface speed due to rotation divided by forward speed; the main control on how large the effect is.DEFINED IN Magnus effect
Spinoff: A new firm founded by former employees of an existing one, typically nearby and in the same trade.DEFINED IN Industrial district persistence
Split: The unit of work a query engine assigns to one worker, often a file or a row group.DEFINED IN The small files problem
Split brain: The state in which two nodes both believe they hold an exclusive role.DEFINED IN Dead or just slow? · Distributed consensus · Quorums
Split-attention effect: The learning penalty from separating two sources that must be mentally integrated to be understood.DEFINED IN Split attention in materials
Split-brain: A state in which two or more nodes each believe they hold exclusive leadership, typically after a network partition or a process pause.DEFINED IN Split-brain
Split-view poisoning: Exploiting the gap between what a dataset's listed URL served when crawled and what it serves when later downloaded.DEFINED IN Poisoning the well
Spo0A: The master regulator whose activation, through a multi-step phosphorelay, commits a cell to the sporulation pathway.DEFINED IN Bacterial dormancy
Spoke: An outlying city connected to the network only through the hub.DEFINED IN Hub-and-spoke routing
Spontaneous recovery: The return of a habituated response after a period without the stimulus.DEFINED IN Habituation versus sensitization
Spread zone: A region periodically overrun by a single expanding language, leaving low diversity and shallow time depth.DEFINED IN Mountain language diversity
Spring and neap tides: The larger and smaller tides produced when the Sun's tidal effect adds to, or works across, the Moon's.DEFINED IN Twice-daily tides
Square-cube law: As a shape is scaled up, area grows as the square of linear size while volume and mass grow as the cube.DEFINED IN Land size limits
Square-root biased sampling: Selecting in proportion to the square root of estimated risk rather than to risk itself.DEFINED IN Randomized screening
Squeeze film: Pressure generated by two surfaces approaching, carrying load transiently with no sliding.DEFINED IN Oil film in bearings
Stabilisation: The tasks of maintaining order and basic services after organised resistance ends.DEFINED IN Holding conquered ground
Stabiliser: An additive, here acidic, kept in slight excess to quench initiations during storage.DEFINED IN Instant glue
Stability: A property of an algorithm: whether it introduces error beyond what the problem's conditioning makes unavoidable.DEFINED IN Catastrophic cancellation
Stack effect: The pressure difference driving air through a building because warm indoor air is buoyant.DEFINED IN House dust
Stack height limit: A regulation capping the thickness of a running shoe's sole, used in place of prohibiting energy-returning shoes.DEFINED IN Equipment bans in sport
Staged authenticity: MacCannell's term for a back region opened to visitors, which thereby becomes a front region designed to look unstaged.DEFINED IN Authenticity
Staging: Arranging a scene for the camera, which alters what the photograph is evidence of without falsifying the photograph itself.DEFINED IN Photographic evidence
Stale claim: A statement that was true of the code at generation time and may not be now.DEFINED IN Documentation that points at its evidence
Staleness window: The accepted maximum lag between a copy and the source it reflects.DEFINED IN Denormalization
Standard: A test whose content is supplied at the moment of application, such as reasonableness or good faith.DEFINED IN Bright-line rules
Standard candle: An object whose true luminosity can be inferred from an observable property, so its dimness gives its distance.DEFINED IN Cosmic distance ladder
Standard error: The typical spread of an estimate across repeated samples; for a proportion, √(p(1 − p)/n).DEFINED IN Sample size versus population
Standard error of the mean: The typical spread of a sample average around the true value, equal to the population standard deviation divided by sqrt(n).DEFINED IN Error cancellation in averages
Standard germination test: A legally recognised procedure counting normal seedlings under optimal, controlled conditions.DEFINED IN Seed vigour versus germination
Standard gravitational parameter (GM): The product of the gravitational constant and a body's mass, measured far more precisely than either factor alone.DEFINED IN Orbital drag speed-up
Standard of proof: The degree of certainty required: beyond reasonable doubt, or the balance of probabilities.DEFINED IN Presumption of innocence
Standard time: A single clock adopted across a region regardless of local solar time.DEFINED IN Time zones
Star schema: A central fact table joined directly to denormalised dimension tables, each one hop away.DEFINED IN The untidy shape that answers faster
Stare decisis: The principle of standing by decided matters; following earlier decisions.DEFINED IN Legal precedent
Start-up lost time: The seconds at the start of each green during which the queue accelerates and passes fewer vehicles than saturation flow.DEFINED IN Green wave signal timing
State: A version of a plate after the artist has deliberately altered it, as distinct from the gradual wear within one version.DEFINED IN Drypoint burr
State of exception: A legally declared condition in which ordinary constraints on executive action are suspended or relaxed.DEFINED IN Emergency powers ratchet
state` parameter: A client-generated value echoed back on the redirect, used to tie the response to the request the client's own session made.DEFINED IN Proving you started the exchange you are finishing
Stateless tier: A layer whose machines hold no data another would need, which is what makes it cheap to replicate.DEFINED IN Vertical and horizontal scaling
States that are essentially by-products: Elster's term for conditions that cannot be brought about by intending them, because the intention is part of what excludes them.DEFINED IN Self-defeating aims
Static batching: Forming a fixed group and running it to completion, so every member waits for the longest.DEFINED IN Batching and the throughput trade
Static deflection: How far a mount squashes under the weight it carries; the practical proxy for softness on a datasheet.DEFINED IN Vibration isolator resonance
Static fatigue: Delayed failure of glass under sustained load, driven by moisture-assisted slow crack growth.DEFINED IN Fibre strength and flaws
Static stability: Designing the data plane to keep operating correctly on its last known configuration when the control plane is unavailable.DEFINED IN Control plane and data plane
Statically indeterminate: Having more unknown support forces than equilibrium equations, so the loads depend on how the parts flex.DEFINED IN Wobbly table
Station-keeping: The small periodic burns that cancel accumulated drift away from an unstable point.DEFINED IN Lagrange points
Stationary distribution: A distribution π with π*P* = π, unchanged by another step of the chain.DEFINED IN Long-run chain behaviour
Stationary phase: The water bound to the cellulose, together with the cellulose surface itself, which does not move.DEFINED IN Paper chromatography
Statistical approximation error: Distortion introduced purely because each generation trains on a finite sample, systematically losing low-probability cases.DEFINED IN Model collapse
Statistical multiplexing: Selling more aggregate peak than you own, relying on peaks rarely coinciding.DEFINED IN The noisy neighbour
Statistical self-similarity: The property of looking about equally rough at many scales without repeating exactly.DEFINED IN Coastline paradox
Status quo bias: The preference for the outcome that requires no action, which here is always keeping.DEFINED IN Clutter
Statute of Artificers (1563): English legislation that made a seven-year apprenticeship a legal requirement across a wide range of trades.DEFINED IN Apprenticeship indentures
Statute of Labourers: English legislation of 1351, following the 1349 Ordinance, capping wages at pre-plague levels and restricting movement between employers.DEFINED IN Post-plague wages
Statutory incidence: The party the law obliges to remit the tax.DEFINED IN Tax incidence
Steady state: A condition held constant by continuous input rather than by the absence of change.DEFINED IN Sourdough stability · Steady-state dosing
Steady-state hypothesis: A measurable statement of normal system behaviour, usually a business-level output, predicted to hold while a failure is injected.DEFINED IN Chaos engineering
Steady-state offset: The permanent gap left by proportional-only control, since nonzero output requires nonzero error.DEFINED IN Feedback control
Stefan-Boltzmann law: The rule that radiated power per unit area rises as the fourth power of absolute temperature.DEFINED IN Spacecraft cooling
Steiner triple system: A set of triples from n points in which every pair of points appears in exactly one triple.DEFINED IN Block design existence
Stellar occultation: The passage of a body in front of a background star, whose gradual dimming reveals the atmosphere's structure.DEFINED IN Pluto's seasonal atmosphere
Stemming: Reducing words to a common root so related forms share an index entry.DEFINED IN Search indexing
Sterbenz's lemma: The result that a − b is exact in binary floating point whenever a and b lie within a factor of two of each other.DEFINED IN Catastrophic cancellation
Sterile cockpit rule: An aviation rule barring non-essential conversation during critical phases of flight, below ten thousand feet.DEFINED IN Shift handover
Sterilizing immunity: Immunity that prevents infection and onward transmission, not merely severe disease.DEFINED IN Herd immunity
Stevens' power law: The power functions fitted to direct magnitude estimates, with a different exponent per sense.DEFINED IN Just-noticeable difference
Stick-slip motion: The alternating grip and release of bow on string that makes a bowed note self-sustaining.DEFINED IN Cello wolf tone
Stiffening girder: The deck's own truss or box, distributing concentrated and wind loads so the flexible cable holds its designed shape.DEFINED IN Suspension bridge cables
Stigmergy: Coordination in which individuals communicate by modifying a shared environment rather than each other.DEFINED IN Collective ant behavior
Stimulated emission: An excited atom induced by a passing photon to emit a second matching it in phase, direction, polarisation and frequency.DEFINED IN Laser coherence
Stint: A quantified limit on how much a commoner may graze, often tied to their private winter fodder capacity.DEFINED IN Common high pasture
Stock-association: A durable partnership between herders in which animals are placed with one another, the owner retaining title.DEFINED IN Herd dispersal among kin
Stokes regime: The low-speed, viscosity-dominated case where drag is proportional to speed rather than its square, governing cloud droplets.DEFINED IN Terminal velocity of raindrops
Stoma: A pore in the leaf surface, bounded by two guard cells, through which carbon dioxide enters and water vapour leaves.DEFINED IN Midday stomatal closure
Stop words: Very common terms sometimes excluded from an index for carrying little discriminating power.DEFINED IN Search indexing
Stop-and-go wave: A band of stopped or slow traffic that propagates upstream while the vehicles in it move downstream.DEFINED IN Phantom traffic jams
Stop-drilling: Arresting a crack by drilling a round hole at its tip, replacing a sharp radius with a blunt one.DEFINED IN Stress concentration
Storage limitation: The GDPR principle, Article 5(1)(e), that personal data be kept in identifiable form no longer than necessary.DEFINED IN Data you keep is data you can lose
Storage strength versus retrieval strength: The distinction between how well something is learned and how accessible it currently is.DEFINED IN Retrieval practice
Stored-product pest: An insect whose ecology is built around human food stores rather than the field or the wild.DEFINED IN Pantry moth persistence
Stranding surface: An ablation zone where obstructed ice flow delivers englacial debris, including meteorites, to the surface.DEFINED IN Antarctic meteorite concentration
Strange Situation: Ainsworth's laboratory procedure of brief separations and reunions in an unfamiliar room, used to classify a caregiver-infant relationship.DEFINED IN Attachment
Strangler fig pattern: Incrementally replacing a system by routing traffic piece by piece to a new one until nothing reaches the old.DEFINED IN Choosing the first piece to replace · Replacing a system you cannot turn off
Strategic interaction: Arreguin-Toft's argument that outcomes depend on how each side's direct or indirect approach meets the other's, not on force ratios alone.DEFINED IN Asymmetric warfare
Strategic misrepresentation: Deliberately optimistic forecasting to secure approval or funding, as distinct from cognitive bias.DEFINED IN Planning fallacy
Stratification: The stable layering of a water body by density, resisting vertical mixing.DEFINED IN Lake turnover
Stream-table duality: A stream of keyed changes and a table of current values as two views of one thing.DEFINED IN Keeping the history and the snapshot in one file
Stress: Force per unit area at a point in a material; what the edge is really delivering.DEFINED IN Sharpness
Stress concentration factor (Kt): The ratio of peak local stress at a geometric feature to the nominal stress away from it, fixed by shape alone.DEFINED IN Stress concentration
Stress intensity factor (K): A single quantity combining applied stress and crack size to describe the severity of the crack-tip field.DEFINED IN Leak-before-break
Stribeck curve: The plot of friction against viscosity times speed divided by load, showing the boundary, mixed and full-film regimes.DEFINED IN Oil film in bearings
Strickle: A straight stick drawn across a measure's rim to level the contents, converting a heaped measure into a struck one.DEFINED IN Measurement standardization
String instability: The property of a line of vehicles in which a disturbance grows as it passes from each follower to the next.DEFINED IN Phantom traffic jams
Stroke contrast: The ratio between a letter's thickest and thinnest strokes, the first thing a small size cannot afford.DEFINED IN Optical sizes in type
Strong-form review: Review in which a judicial ruling of unconstitutionality voids the statute.DEFINED IN Judicial review
Strouhal number: The group St = fD/U, near 0.2 for a circular cylinder over a wide range of Reynolds number.DEFINED IN Vortex shedding
Structural attrition: The loss of social ties through death, retirement, illness or relocation, as distinct from ties given up by choice.DEFINED IN Shrinking social circles
Structured discretion: Discretion constrained by published criteria, recorded reasons and audit rather than removed.DEFINED IN Enforcement discretion
Study-phase retrieval: The account that a spaced repetition works by prompting retrieval of the earlier episode, which strengthens it.DEFINED IN Spacing effect
Subacute ruminal acidosis: A sustained depression of rumen pH from rapidly fermentable starch, which itself reduces intake.DEFINED IN Dairy cow energy balance
Suberogatory: Driver's mirror category: an act that is bad and criticisable yet still permitted.DEFINED IN Supererogation
Sublimation: A solid passing directly to gas without melting, the process that switches a comet on near the Sun.DEFINED IN Comet tails · Evaporative drying · Freezer burn · Pluto's seasonal atmosphere
Sublimator: A device that dumps heat by letting water pass straight to vapour into vacuum, used where radiating area is unavailable.DEFINED IN Spacecraft cooling
Subsidence: Large-scale sinking air, which warms by compression and suppresses cloud formation.DEFINED IN Desert latitudes
Subsidence inversion: A layer of descending, warming air that caps the moist marine layer from above.DEFINED IN Coastal fog belts
Substantive canon: A presumption favouring a particular outcome, such as lenity in criminal statutes, rather than a convention about language.DEFINED IN Statutory interpretation canons
Substitutability: Whether another producer could make the missing item, and how fast; what sets recovery time.DEFINED IN Just-in-time fragility
Substitution effect: A stocked-out customer's switch to another item, which inflates that item's recorded sales.DEFINED IN Stockout demand censoring
Substrate: The first languages of the speakers who formed the contact variety, whose patterns can persist under lexifier words.DEFINED IN Creole genesis · Twenty-five acronyms, nine pieces
Subtractive mixing: Combining absorbers in a fixed illumination, so each removes a band and the result is darker.DEFINED IN Color mixing
Subtropical high: The belt of persistent surface high pressure produced by that descent.DEFINED IN Desert latitudes
Sufficient interest: The looser English test for standing in judicial review, which admits public-interest applicants.DEFINED IN Standing to sue
Sunk cost: Money already spent and unrecoverable, which should not bear on a present decision but reliably does.DEFINED IN Clutter · Industry concentration · Sunk cost
Sunk cost fallacy: Letting such an expenditure influence a choice between futures it cannot distinguish.DEFINED IN Sunk cost
Sunset clause: A provision causing a rule to expire on a fixed date unless it is affirmatively renewed.DEFINED IN Persistent rules
Sunset provision: A clause causing a law to expire on a stated date unless renewed.DEFINED IN Budget scoring windows
Superadditive values: Values for which a set of items is worth more than the sum of its members; the precondition for exposure.DEFINED IN Exposure problem in package bidding
Supercompensation: The rise in performance above the pre-training level as recovery outpaces the loss of adaptation.DEFINED IN Training taper
Superelasticity: Large recoverable deformation above the austenite temperature, where stress rather than cooling produces the martensite.DEFINED IN Shape-memory alloys
Supererogation: An act that is morally good and praiseworthy but not required, so omitting it is not wrong.DEFINED IN Supererogation
Superiority theory: The older account, traceable to Hobbes and earlier, that laughter expresses a sudden sense of advantage over someone.DEFINED IN Explained jokes
Superrotation: An atmosphere carrying more angular momentum per unit mass than the surface beneath it.DEFINED IN Venus superrotation
Supersaturation: Holding more dissolved gas than equilibrium allows, the condition that makes bubbles appear.DEFINED IN Cloudy ice cubes
Supersession: Marking an older claim as replaced by a newer one, rather than storing both as equals.DEFINED IN What an assistant should forget
Superstrate: A socially dominant language superposed on another, as Norman French was on English.DEFINED IN Loanword doublets
Supervision tree: A hierarchy of processes whose job is to restart failed children from a known state, the partner mechanism that makes failing fast affordable.DEFINED IN Failing fast
Supply line: Orders placed but not yet received; ignoring it is the classic source of over-ordering.DEFINED IN Bullwhip effect
Support polygon: The shape enclosed by the contact points; an object tips when its weight line leaves it.DEFINED IN Wobbly table
Suprachiasmatic nucleus: The small hypothalamic cluster that acts as the body's master circadian pacemaker.DEFINED IN Dawn light and the body clock · Jet lag
Surface albedo feedback: The loss of reflective snow and ice exposing darker surfaces that absorb more sunlight.DEFINED IN Polar amplification
Surface features: The concrete details of a problem, which drive retrieval even when they are irrelevant.DEFINED IN Transfer of learning
Surface law: Rubner's proposal that metabolic rate tracks heat-losing surface area, predicting a two-thirds exponent.DEFINED IN Metabolic scaling
Surface premelting: Formation of a disordered, liquid-like layer on a solid's surface below its bulk melting point.DEFINED IN Slippery ice
Surface seal or crust: A thin dense layer formed when raindrop impact breaks aggregates and fines block the pores beneath.DEFINED IN Runoff from dry ground
Surface tension: The force per unit length acting along a liquid surface, set by the liquid's composition rather than by how far the surface has been stretched.DEFINED IN Tears of wine · Terminal velocity of raindrops
Surfactant: A molecule with a water-attracting end and a water-repelled end, which gathers at boundaries.DEFINED IN Soap cleaning
Surge-type glacier: A glacier that alternates between long slow phases and short episodes of greatly accelerated flow.DEFINED IN Glacier flow
Surprise: The advantage arising specifically from an opponent being arranged for a different threat, and therefore consumable.DEFINED IN Fading advantage of a new weapon
Surrogate key: An identifier minted by the storing system, carrying no business meaning, used as the target of references.DEFINED IN Surrogate keys
Survivorship bias: Drawing conclusions from a sample that only contains those who remained, so the departed cannot be observed.DEFINED IN Early sport specialization · Survivorship bias
Survivorship rules: Per-attribute rules choosing which source's value appears in the mastered record.DEFINED IN Which record is the real one
Suspension: Cutting a word off after its opening letters and marking the loss with a stroke.DEFINED IN Scribal abbreviation
Sustaining innovation: An improvement along dimensions existing customers already value; historically won by incumbents.DEFINED IN Incumbent disruption
Swallet: The hole, also called a sink or ponor, where a surface stream enters the limestone.DEFINED IN Sinking streams in karst
Swidden: Shifting cultivation in which plots are cleared, farmed briefly and left to regrow, typically with root crops rather than grain.DEFINED IN Origin of the state
Swing ratio: The duration of the first note of a pair divided by the second, in a swung subdivision.DEFINED IN Groove and microtiming
Switching cost: Everything that must be paid again to move off an established convention, including tooling, training and complements.DEFINED IN Technical standards · The price of being able to leave
Symbiodiniaceae: The family of single-celled algae living inside coral tissue and supplying most of the animal's energy.DEFINED IN Coral bleaching
Symmetric cipher: An ordinary shared-key cipher, fast enough to carry the traffic once a key has been agreed.DEFINED IN How encryption keeps messages secret
Symptom-based alerting: Paging on user-visible harm rather than on internal causes, to reduce alert volume and raise the fraction that are actionable.DEFINED IN Alert fatigue
Synchroniser token: An unguessable per-session value embedded in a site's own forms and verified on submission.DEFINED IN Requests you did not make
Synchronous replication: Acknowledging a write only after it is durable in more than one place; drives RPO toward zero at the cost of write latency.DEFINED IN Recovery objectives
Syncopation: Placing notes away from the strong beats, so the played pattern and the felt pulse diverge.DEFINED IN Groove and microtiming
Syncytiotrophoblast: The fused, boundary-free fetal layer in direct contact with maternal blood.DEFINED IN Pregnancy immune tolerance
Synodic month: The interval from new moon to new moon, about 29.53 days.DEFINED IN Calendar drift
Synoptic wind: The large-scale wind field of the day's weather systems, which can overwhelm local circulations.DEFINED IN Sea breeze reversal
Syntactic bootstrapping: Using a sentence's grammatical frame to constrain what kind of thing a new word could mean.DEFINED IN Child word learning
Synthetic monitoring: Scripted transactions run on a schedule from controlled locations, giving a stable baseline independent of real traffic.DEFINED IN Synthetic versus real users
System inertia: The total rotational kinetic energy of synchronised machines, which resists changes in grid frequency.DEFINED IN Grid balancing
System prompt: Instructions placed ahead of the conversation on every request, which consume window budget like any other text.DEFINED IN Context window · System prompt priority
Systematic error (bias): A consistent offset in one direction, which averaging leaves untouched.DEFINED IN Error cancellation in averages
Szilard engine: A one-molecule box in which knowing which half the molecule occupies yields kT ln 2 of work.DEFINED IN Maxwell's demon

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T cell: The lineage that directs the response and kills your own already-infected cells.DEFINED IN How vaccines work
Taboo trade-off: A comparison between a sacred value and a secular one, whose mere contemplation provokes moral outrage.DEFINED IN Pricing the sacred
Tabulation: The bottom-up form of dynamic programming: fill a table in dependency order rather than caching a recursion.DEFINED IN Remembering the sub-answers
Tacit knowledge: Working understanding that is demonstrated rather than written, and so travels mainly with people.DEFINED IN Industrial district persistence · Learning a trade by standing there · Technology loss · Working to rule
Taenite: The nickel-rich, face-centred-cubic phase of iron-nickel alloy, stable at high temperature.DEFINED IN Widmanstatten pattern
Tag: A mutable, human-readable label within a repository that points at one manifest digest.DEFINED IN Tags versus digests
Tail exponent (alpha): The power governing that decay; the mean exists only above 1, the variance only above 2.DEFINED IN Unstable averages
Tail latency: The high percentiles of a latency distribution, such as the 99th or 99.9th, as opposed to its mean or median.DEFINED IN Tail latency
Tail-based sampling: Deciding whether to keep a trace after it completes, so slow and failed traces can be retained preferentially.DEFINED IN Distributed tracing
Talent identification: Systematic screening of a population for the physiology an event rewards, rather than waiting for self-selection.DEFINED IN Falling records
Talik: An unfrozen zone within or beneath permafrost, typically maintained by the insulating effect of a lake.DEFINED IN Pingo growth
Tamper-evident log: A record structured, typically by chaining entries with hashes, so that any later alteration is detectable.DEFINED IN The audit record as the product
Tangent vector field: An assignment of an arrow lying in the surface to each of its points.DEFINED IN Hairy ball theorem
Tankering: Uplifting more fuel than the sector needs where it is cheaper, accepting the carriage penalty to avoid buying at a dearer airport.DEFINED IN Contingency fuel
Taper: A planned reduction in training load before competition, typically cutting volume while preserving intensity and frequency.DEFINED IN Training taper · Whip crack
Taphonomy: The study of what happens to material between its use and its recovery, treated as a process with its own laws.DEFINED IN Preservation bias
Targeted sanctions: Measures aimed at named individuals or entities rather than at a national economy.DEFINED IN Blockade and resolve
Task-contingent reward: A reward given for performing an activity at all, as distinct from one given for how well it was done.DEFINED IN Paying pupils to read
Teacher forcing: Training a model by always feeding it the true prefix rather than its own output.DEFINED IN One improbable word
Teaching expectancy: The manipulation of telling learners they will later teach the material, without their necessarily doing so.DEFINED IN Learning by explaining
Technical debt: The future cost of choosing an expedient implementation over a better-structured one.DEFINED IN Technical debt
Teetering hub: A hinged hub letting a two-bladed rotor rock, absorbing the cyclic loads blade symmetry would otherwise prevent.DEFINED IN Three-bladed turbines
Teleoanticipation: The proposal that pace is regulated in advance from the distance remaining rather than by failure at the limit.DEFINED IN Even pacing
Temperance: Aristotle's state in which the appetites themselves are correctly ordered, so no contrary pull arises.DEFINED IN Effortless virtue
Temperate (warm-based) glacier: One whose ice is at the melting point throughout, including at the bed.DEFINED IN Glacier flow
Temperature: A parameter that sharpens or flattens the distribution before sampling; zero means always take the most likely token.DEFINED IN One improbable word · Prompt sensitivity · Self-consistency
Temperature and truncation: Generation-time settings that suppress unlikely tokens to improve quality, and in doing so remove the distribution's tails.DEFINED IN Model collapse
Temperature inversion: An atmospheric layer in which temperature rises with height, suppressing convection and trapping heat low down.DEFINED IN Polar amplification · Radiation frost
Temperature minimum: The daily low point of core body temperature, late in the biological night, used as the reference marker for internal phase.DEFINED IN Dawn light and the body clock
Temperature scaling: A one-parameter post-hoc adjustment that flattens a model's output distribution to improve calibration without changing its ranking of answers.DEFINED IN Confident model errors
Tempering: A controlled reheat that relaxes some of that strain, exchanging hardness for toughness.DEFINED IN Alloy strength
Temporal coherence: Correlation of phase over time, equivalent to narrowness in wavelength, measured as a coherence length.DEFINED IN Laser coherence
Temporal locality: The empirical tendency of recently used items to be used again soon.DEFINED IN Choosing what to forget
Temporary hardness: Hardness carried as bicarbonate, removable by boiling, which is what becomes kettle scale.DEFINED IN Limescale
Tendinopathy: Chronic tendon pain and dysfunction with matrix disorganisation rather than classical inflammation.DEFINED IN Tendon rehabilitation loading
Tenocyte: The resident tendon cell that senses matrix strain and adjusts collagen synthesis.DEFINED IN Tendon rehabilitation loading
Tensile strength: The pull a material withstands before separating; for stone it is far lower than its resistance to being squashed.DEFINED IN Marble supports
Tenting: Compressive buckling of a bonded tile field, in which tiles debond and arch up in a ridge.DEFINED IN Movement joints in tiling
Tenure: The legal basis on which someone occupies a property: freehold, leasehold, regulated tenancy, tenancy at will.DEFINED IN Gentrification
Term / epoch: A monotonically increasing number identifying a leadership period, used to reject stale commands.DEFINED IN Distributed consensus
Term limit: A statutory or constitutional cap on how long a person may hold a given office.DEFINED IN Term limits
Term of art: An ordinary-looking word given a fixed, bounded technical sense within a field, such as consideration in contract law.DEFINED IN Trade jargon
Terminal lake: The water body at the end of an endorheic system, whose area adjusts until evaporation balances inflow.DEFINED IN Endorheic basins
Terminal velocity: The constant speed at which drag exactly cancels weight, so acceleration stops.DEFINED IN Terminal velocity of raindrops
Terminal velocity on a slope: The coasting speed at which gravity's component along the road isDEFINED IN Climbing versus descending weight
Terms of trade: The ratio at which the goods are actually exchanged, which decides how the gains are divided.DEFINED IN Comparative advantage
Terrestrial age: How long a meteorite has lain on Earth since it fell, measured from the decay of isotopes produced only during its exposure in space.DEFINED IN Antarctic meteorite concentration
Test pyramid: The heuristic, introduced by Mike Cohn in 2009, that a suite should hold many fast narrow tests, fewer service-level tests, and few end-to-end tests.DEFINED IN The test pyramid
Test-driven development: Writing the test before the implementation, so the interface is designed from the caller's side.DEFINED IN Testability as a design property · Writing the test first
Test-time compute: Computation spent when answering, as opposed to during training.DEFINED IN Thinking budget
Testability: How cheaply code can be placed in a known state, executed, and observed.DEFINED IN Testability as a design property
Testimony: A claim believed on the ground that someone asserted it, in speech or writing.DEFINED IN Knowledge from testimony
Testing effect: The finding that attempting to recall material improves later retention more than restudying it for the same time.DEFINED IN Retrieval practice
Testing trophy: Kent C. Dodds' counter-proposal, weighting integration tests most heavily for typical web applications.DEFINED IN The test pyramid
TF-IDF: A weighting that rewards terms frequent in a document and rare across the collection.DEFINED IN Search indexing
Thalamus: The sensory relay through which vision, hearing and touch must pass before reaching cortex.DEFINED IN Smell and memory
Thalweg: The deepest channel of a river, often used as the boundary line so navigation rights stay workable.DEFINED IN Borders · River boundaries that shift
The simple view of reading: The framing of reading comprehension as decoding multiplied by language comprehension, so that either factor can be limiting.DEFINED IN Knowledge and comprehension
The three obligations: Mauss's claim that gift systems compel giving, receiving and repaying, each with its own sanction for refusal.DEFINED IN Gift obligation
Theorema Egregium: Gauss's result that a surface's curvature is measurable from within it, and so cannot be changed by bending without stretching.DEFINED IN Map projection distortion
Theoretical virtues: Simplicity, scope, consistency and fruitfulness, cited in theory choice when evidence does not decide.DEFINED IN Underdetermination of theory
Theory of descriptions: Russell's analysis recasting apparent subject-predicate claims as existential ones.DEFINED IN Talking about what does not exist
Theory X: Parfit's label for the satisfactory theory of population ethics he sought and did not find.DEFINED IN Non-identity problem
Therapeutic index: The ratio of the toxic dose to the effective dose; a rough measure of how wide the window is.DEFINED IN Dose-response
Therapeutic window: The range of doses at which a substance produces the desired effect without unacceptable harm.DEFINED IN Dose-response
Thermal conductance: How readily a building element passes heat, per unit area and per degree of temperature difference.DEFINED IN Home insulation
Thermal conductivity: How readily a material passes heat along, in watts per metre per kelvin.DEFINED IN Thermal conductivity of touch
Thermal cracking: Transverse cracking caused by tensile stress in a restrained surfacing as it contracts in cold weather.DEFINED IN Road cracking
Thermal diffusivity (α): Conductivity divided by volumetric heat capacity, in square metres per second; the single material number that sets how fast a temperature change spreads.DEFINED IN Heat diffusion time
Thermal effusivity: A material's rate of drawing heat from a warmer body in contact with it, which is why stone feels colder than wood at the same temperature.DEFINED IN Architectural atmosphere · Cold floors · Thermal conductivity of touch
Thermal inertia: A surface's resistance to changing temperature, which sets how far past noon the daily peak is carried.DEFINED IN Yarkovsky effect
Thermal lag: The delay between a temperature change at one face of a solid and the response at the other.DEFINED IN Heat diffusion time · Night-time alarm chirp
Thermal mass: The heat a package and heatsink can absorb while warming, which is what makes a short burst above the sustainable power possible.DEFINED IN Thermal throttling
Thermal resistance: How many degrees of temperature difference each watt needs in order to cross a barrier.DEFINED IN Coiled extension lead · Home insulation · Thermal throttling
Thermal skin depth: The depth to which a periodic surface temperature swing penetrates a solid, growing as the square root of the period.DEFINED IN Pluto's seasonal atmosphere
Thermal tide: A planetary-scale wave excited by a heating pattern that moves with the Sun rather than with the solid body.DEFINED IN Venus superrotation
Thermally direct circulation: A flow driven by a horizontal temperature difference, with warm air rising and cool air sinking.DEFINED IN Sea breeze reversal
Thermionic emission: Release of electrons from a hot surface, which in an arc replaces the far more voltage-hungry ion bombardment of a cold cathode.DEFINED IN Ballast in a gas discharge
Thermocline: The sharp boundary between the warm surface layer and the cold deep water; its depth decides how cold upwelled water is.DEFINED IN El Nino oscillation · Lake turnover · Ocean productivity
Thermohaline circulation: The deep overturning driven by density differences arising from temperature and salinity.DEFINED IN Ocean circulation
Thermophilic: Describing organisms that grow best at high temperatures, roughly 45 degrees Celsius and above; they dominate a compost core once it warms.DEFINED IN Compost heat
Thermoregulatory hypothesis: The proposal that yawning cools the brain; contested, with thin and largely correlational support.DEFINED IN Contagious yawning
Thin-film interference: Colour produced by two reflections from the faces of a film recombining in or out of step.DEFINED IN Soap film colours
Think-pair-share: A format in which students first work alone, then with one partner, before anything is said to the whole room.DEFINED IN The silent classroom
Thinking budget: A cap on the tokens a reasoning model may spend working before it replies.DEFINED IN Thinking budget
Third normal form: Every non-key column depends on the key, the whole key, and nothing but the key.DEFINED IN Normalization
Third-party reporting: Income reported to the authority by an employer, bank or platform as well as by the taxpayer.DEFINED IN Random audits
Three-body reaction: A combination needing a bystander to remove energy, adding a factor of pressure.DEFINED IN Chain-branching explosion limits
Three-phase commit: A variant that avoids blocking under bounded-delay crash failures but is unsafe under network partitions.DEFINED IN The blocking commit
Three-way merge: Combining two versions by comparing each against their common ancestor rather than against each other.DEFINED IN Merge conflicts
Threshing floor: The open ground where a cereal harvest is beaten and winnowed, and where the whole year's crop briefly sits in one visible heap.DEFINED IN Grain and taxation
Threshold: The minimum catchment a trade needs to survive, which an itinerant seller can meet by summing several places.DEFINED IN Market day rotation · Town spacing
Threshold effect: An outcome that stays absent while a hidden quantity accumulates, then appears in full once that quantity crosses a limit.DEFINED IN The small last straw
Threshold population: The minimum catchment a service needs to be viable, below which it closes rather than shrinks.DEFINED IN Rural depopulation
Threshold rule: The assumption that an effect below the level of detection counts as no effect at all.DEFINED IN Imperceptible harms · Video review boundaries
Thrift (economy): The tendency of a formulaic system to hold roughly one phrase for each metrical slot and function.DEFINED IN Formulaic oral composition
Throughput: How much a port, railhead, or road can actually move per day, usually a tighter limit than how much exists to be moved.DEFINED IN Military logistics
Tidal bulge: The stretching caused by gravity pulling harder on a body's near side than its far side.DEFINED IN Tidal locking
Tidal force: The difference in gravitational pull across an extended body, which stretches it along the line to the attracting object.DEFINED IN Planetary rings · Twice-daily tides · What is a black hole?
Tied request: A request enqueued on two replicas at once, each carrying the other's identity so whichever starts first cancels its twin.DEFINED IN Tail latency
Timbre: The tone colour of a sound, set by the relative strengths of its components rather than by its fundamental frequency.DEFINED IN Helium voice · How can music create emotion?
Time horizon: A person's sense of how much time lies ahead, which the theory treats as the causal variable rather than chronological age.DEFINED IN Shrinking social circles
Time preference: The premium placed on having resources now rather than later; one of the three components of interest.DEFINED IN Credit
Time to first token: Elapsed time from request to the first visible output; the interval users perceive as the wait.DEFINED IN Time to first token
Time travel: Reading a table as of an earlier snapshot, possible because its files were never modified.DEFINED IN Transactions on immutable storage
Time-based prospective memory: An intention that must be retrieved at or by a clock time, with no external cue to trigger it.DEFINED IN Prospective memory
Time-boxed suspension: Deliberately stopping a practice for a fixed period, with a pre-agreed signal that would justify reinstating it.DEFINED IN Ceremony as a smell
Timing: The control of when the punchline lands, which determines whether the hearer has committed to the first reading and whether the second arrives all at once.DEFINED IN Explained jokes
tini: A minimal init program that forwards signals to its child and reaps orphaned processes.DEFINED IN The first process
Tip credit: A legal provision letting an employer count an employee's tips toward the statutory minimum wage.DEFINED IN Tipping customs
Tip-speed ratio: Blade tip speed divided by wind speed, trading blade count against rotational speed.DEFINED IN Three-bladed turbines
Tipping: The tendency of a market with positive feedback to run toward a single dominant option rather than a stable split.DEFINED IN Network effects
Tironian notes: An ancient Latin shorthand system, some of whose signs medieval scribes absorbed, including the et sign.DEFINED IN Scribal abbreviation
Tissot's indicatrix: A tiny circle on the globe drawn as the map renders it, showing local distortion as an ellipse.DEFINED IN Map projection distortion
Tissue acidosis: The lowered pH of inflamed tissue, produced by inflammatory metabolism and local ischaemia.DEFINED IN Local anaesthetic failure
Token: The unit a model actually predicts: a subword fragment from a fixed vocabulary, not a word.DEFINED IN Next-token prediction · Tokenization
Token embedding: The per-token vector table, the one genuinely address-based store in the model.DEFINED IN Where a fact lives in a model
Token family: The chain of tokens descended from a single grant, revoked together when reuse is detected.DEFINED IN Detecting a theft you cannot see
Token introspection (RFC 7662): An endpoint at which a verifier asks the issuer whether a given token is currently active.DEFINED IN You cannot un-issue a signature
Tokenisation: Splitting text into indexable units, a decision that must match between indexing and querying.DEFINED IN Search indexing
Tolerance chain: The sequence of dimensions between the two features whose relationship the assembly requires.DEFINED IN Tolerance stack-up
Tolerance principle: The premise that a single minimal change cannot flip the application of a vague predicate.DEFINED IN Vagueness
Tolerated scrounging: The reading in which sharing reflects the owner's inability to defend a resource worth less to him than the fight.DEFINED IN Sharing under scarcity
Tolling: Suspending the running of the period, typically during a defendant's absence or a claimant's minority.DEFINED IN Statutes of limitation
Tombstone: A marker left by a deletion that counts as occupied for searching, preserving other keys' probe sequences.DEFINED IN Hash table clustering · Keeping the history and the snapshot in one file
Tonne-kilometre: One tonne of goods carried one kilometre; the unit in which the efficiency of transport modes is compared.DEFINED IN Food miles
Tool: A model-controlled operation, described with a machine-readable input schema so the assistant can call it unaided.DEFINED IN Control as a classification
Tool call: A structured request emitted by a model naming an operation and its arguments.DEFINED IN Tool calling boundary
Toponym: A place name, considered as evidence.DEFINED IN Place names
Torpor: A controlled state of reduced metabolic rate and body temperature; hibernation is a season-long series of torpor bouts.DEFINED IN Hibernation
Torque: A twisting push about an axis; the only thing that can change a body's angular momentum.DEFINED IN Figure-skating spin · Gyroscopic precession · Mechanical advantage · Tidal locking
Total allowable catch: The aggregate landings limit set for a stock in a season.DEFINED IN Race to fish under quota
Total internal reflection: Reflection of all incident light at such a boundary, with no transmitted ray.DEFINED IN Guided light
Toughness: A material's resistance to having a crack start and travel through it.DEFINED IN Sharpness
Tourism area life cycle: Butler's staged model of a destination's development, from exploration through stagnation to decline or rejuvenation.DEFINED IN Overtourism
Tournament theory: The account of promotion as a contest whose prize motivates all entrants, so its incentive value may outweigh its accuracy as a selection device.DEFINED IN Promotion mismatch
Town plan (in morphology): The streets, plots and block pattern, treated as a layer distinct from the buildings on them and changing far more slowly.DEFINED IN Unplanned settlement form
Trace italienne: The low, thick, angular bastioned fortification developed in Italy in the sixteenth century.DEFINED IN Obsolete fortifications
Traceability: The ability to follow a statement back to its origin and forward to what depends on it.DEFINED IN Documentation that points at its evidence
Tracing collector: One that determines liveness by walking references from a set of roots, rather than by tracking counts.DEFINED IN Garbage collection pauses
Trade credit: Goods delivered now against payment later, extended by the seller rather than by a financial institution.DEFINED IN Trade credit
Trade-off hypothesis: The model in which virulence and transmission rise together, so selection settles on an intermediate optimum.DEFINED IN Virulence and transmission
Trail: The distance by which the front tyre's contact patch sits behind the point where the steering axis meets the ground.DEFINED IN Bicycle stability
Trail (of a bicycle): How far the front wheel's ground contact sits behind the steering axis, the usual non-gyroscopic explanation for self-stability.DEFINED IN Gyroscopic precession
Transaction cost: The cost of arranging an exchange rather than of the thing exchanged: search, specification, negotiation, monitoring and enforcement.DEFINED IN Boundaries of the firm
Transactional outbox: Writing an outbound message into the same database transaction as the change it reports, so the two cannot diverge.DEFINED IN Exactly once is a property of the pipeline
Transactive memory: A system in which individuals store items and also store knowledge of who stores which items.DEFINED IN Shared memory in couples
Transferable adversarial example: An input crafted against a substitute model that also fools the original.DEFINED IN Copying something you can only question
Transformation model: A versioned, tested definition of a derived table, typically expressed as SQL and managed by tooling such as dbt.DEFINED IN Where the transform sits
Transient walk: One with a positive chance of never returning.DEFINED IN Random walk recurrence
Transit: The passage of a planet across its star's disc as seen from Earth, dimming it by the ratio of their areas.DEFINED IN Exoplanet detection
Transit state: The country a landlocked state's goods must cross to reach a seaport.DEFINED IN Landlocked disadvantage
Transition matrix: The table of one-step probabilities, each row a distribution over the next state.DEFINED IN Long-run chain behaviour
Transition state: The highest-energy arrangement along a reaction path, at the top of that barrier.DEFINED IN Catalysis · Enzyme specificity
Transition-relevance place: A point where a turn could be complete, and so where a handover legitimately may occur.DEFINED IN Conversation turn-taking
Transitive closure: The derived relation containing every pair connected by any chain of edges, not just direct ones.DEFINED IN A tree in a table of rows · Blast radius
Transitive dependency: A package you depend on only because something you depend on depends on it.DEFINED IN Dependency conflicts
Translation (of relics): The formal moving of a relic from one place to another.DEFINED IN A relic proved false
Transmissibility: The ratio of force reaching the support to force applied by the machine; below 1 is isolation, above 1 amplification.DEFINED IN Vibration isolator resonance
Transmission mode: The route to the next host: direct contact, respiratory, vector-borne, waterborne, or via caregivers.DEFINED IN Virulence and transmission
Transmittance: The fraction of arriving light that passes through rather than being reflected or absorbed.DEFINED IN Night window reflections
Transverse Doppler shift: A relativistic redshift observed even when the source is moving purely sideways, caused by time dilation and absent from the classical account.DEFINED IN Doppler effect
Trap: A bend in a waste pipe holding a plug of water that blocks gas from the sewer side.DEFINED IN Dry drain trap
Trapdoor function: An operation easy to compute and infeasible to reverse, unless you hold one extra secret.DEFINED IN How encryption keeps messages secret
Travel-to-work area: A functional region built by grouping places until a self-containment threshold is met.DEFINED IN Functional versus administrative regions
Travelling salesman problem: Find the shortest closed tour visiting each of n cities exactly once.DEFINED IN Factorial explosion
Tread: The walked surface of the path itself, as distinct from its verges.DEFINED IN Trail braiding
Treeline: The upper limit of closed or upright forest growth, tracking a growing-season temperature threshold.DEFINED IN Mass elevation effect
TRIAC: A semiconductor switch that, once triggered, conducts until the current through it falls below its holding value.DEFINED IN LED dimmer incompatibility
Triage: Sorting patients by the benefit treatment now would produce, relative to the scarce capacity it consumes.DEFINED IN Emergency triage
Trial penalty: The additional sentence typically imposed after conviction at trial compared with a plea to the same conduct.DEFINED IN Plea bargaining
Triboelectric effect: Charge transfer when two materials contact and separate; well documented empirically, incompletely explained microscopically.DEFINED IN Static electricity
Trichromacy: The reduction of an entire spectrum to three signals by three cone types.DEFINED IN Color mixing
Trickle-down (Simmel): The 1904 account of fashion as elites differentiating themselves and lower strata imitating, forcing elites to move on.DEFINED IN Fashion churn
Trickle-up / trickle-across: The empirical corrections: styles also originate in subcultures and spread upward, or diffuse sideways among peers.DEFINED IN Fashion churn
Trie: A tree in which the path from the root spells the key, so no key is stored in any node.DEFINED IN Words stored by their beginnings
Trilateration: Finding a position from measured distances to known points.DEFINED IN How does GPS find your location?
TRIM: A command telling an SSD which logical blocks are no longer in use so its controller can erase them.DEFINED IN File deletion
Trimethylamine oxide: An osmotic-balance compound in marine fish, reduced by some spoilage bacteria to the trimethylamine responsible for the fishy smell.DEFINED IN Fish spoiling fast
Trimmed mean: An average computed after discarding the most extreme observations; stable, but an estimate of a different quantity.DEFINED IN Unstable averages
Triple convergence: Anthony Downs' account of new capacity consumed by simultaneous shifts of route, departure time and mode.DEFINED IN Induced traffic
Triple valve: The valve on each vehicle that compares pipe pressure with local reservoir pressure and applies, holds or releases accordingly.DEFINED IN Fail-safe braking
Tripwire force: A garrison too small to win, stationed so that any attack automatically engages its country.DEFINED IN Deterrence
Trojan: A small body librating around the L4 or L5 point of a planet's orbit.DEFINED IN Lagrange points
Trojan asteroid: A body sharing a planet's orbital period while remaining roughly sixty degrees ahead of or behind it.DEFINED IN Kirkwood gaps
Trophic cascade: An effect that propagates down a food chain, as a predator's influence on herbivores alters the plants.DEFINED IN Keystone species
Trophic level: A step in a food chain, counted by how many transfers separate an organism from the plants.DEFINED IN Trophic cost of meat
Tropical year: The interval governing the seasons, about 365.2422 days.DEFINED IN Calendar drift
TRPA1: An ion channel that opens on heating in these snakes, and serves as a chemical irritant receptor in mammals.DEFINED IN Pit viper infrared sensing
True peak: The maximum level of the reconstructed analogue waveform, which can exceed the highest digital sample value.DEFINED IN Broadcast loudness
True sharing: Genuine contention for the same variable, which layout changes cannot remove.DEFINED IN False sharing
Truncation: The application-side dropping or summarizing of old turns once a transcript no longer fits.DEFINED IN Context window
Trunk-based development: Integrating small changes into a single main branch continuously, rather than maintaining long-lived feature branches.DEFINED IN Feature flags
Trust boundary: The line across which data must be validated, drawn by data flow rather than by ownership.DEFINED IN Output as untrusted input
Tuned mass damper: A large auxiliary mass tuned near the structure's natural frequency, moving out of phase with it to oppose and dissipate motion.DEFINED IN Building sway
Turbidite: The deposit left by such a flow, characteristically fining upward from a coarse base.DEFINED IN Turbidity currents
Turbidity current: A downslope flow of water made denser than its surroundings by suspended sediment.DEFINED IN Turbidity currents
Turn projection: A listener's running prediction of where the current turn will finish, used to time their own start.DEFINED IN Conversation turn-taking
Turnaround: The time an aircraft spends at the gate between arriving on one leg and departing on the next.DEFINED IN Schedule padding
Turnaround day: The day a ship disembarks one set of passengers and embarks the next at its home port, consuming a full day of the loop.DEFINED IN Cruise call clustering
Turning angle: How far the encounter rotates the probe's planet-relative velocity; larger for a closer, slower pass.DEFINED IN Gravity assist
Turnover spillover: Harm from staff churn falling on pupils whose own teacher did not leave, indicating a school-level rather than individual effect.DEFINED IN Teacher attrition in hard schools
Twinning and detwinning: The formation of mirror-related lattice domains, and their growth at each other's expense under stress.DEFINED IN Shape-memory alloys
Two generals problem: The proof that two parties cannot reach certainty about each other's state over a channel that may lose messages.DEFINED IN Exactly once is a property of the pipeline · Idempotent operations · Losing it or doing it twice
Two-level view: Hare's distinction between intuitive rule-governed thinking in the moment and critical reflection about which rules to hold.DEFINED IN Keeping a rule against the case
Two-phase commit: A protocol for committing across several independent machines: correct, but latency-expensive and vulnerable to a stalled coordinator.DEFINED IN Sharding · The blocking commit
Two-phase locking: Acquiring locks as needed and releasing none until the transaction ends.DEFINED IN Database transactions
Two-tier item: A question that asks for an answer and then for the reasoning behind it, so a right answer from a wrong model is visible.DEFINED IN Classroom misconceptions
Type 2 immunity: The branch specialised for expelling large parasites, and the branch allergy runs on.DEFINED IN Allergy
Type-1 overwrite: Updating an attribute in place and keeping no history, correct whenever nobody will ask what the value used to be.DEFINED IN Rapidly changing attributes
Type-II superconductor: One that admits flux above a first critical field as quantized filaments while staying superconducting between them.DEFINED IN Superconducting levitation
Type-scene: A recurring episode with a conventional sequence of elements, such as an arming or a feast, that gives the singer a template.DEFINED IN Oral tradition
Typological number: A conventional figure such as three, seven or forty used where no exact count is claimed.DEFINED IN Metrical verse
Typology: The comparative study of how languages distribute across structural options, such as which orders are common and which are rare.DEFINED IN Word order

U

Ubiquitous language: One vocabulary shared by developers and domain experts within a context, used identically in speech, documents, and code.DEFINED IN Bounded contexts
UHT: Ultra-high-temperature treatment plus aseptic filling, yielding a commercially sterile package stable at room temperature.DEFINED IN Milk spoilage after opening
Ultimate pH: The acidity a muscle settles at after slaughter, set by how much glycogen was available to ferment to lactic acid.DEFINED IN Fish spoiling fast
Umami: The savoury taste quality associated with glutamates and nucleotides, prominent in tomato, cheese and stock.DEFINED IN Inflight taste
Umpire's call: Cricket's convention of leaving the on-field decision standing when a projected margin falls inside a declared tolerance.DEFINED IN Video review boundaries
Unaccompanied baggage: A bag travelling without its owner, permitted only after additional security controls.DEFINED IN Baggage reconciliation
Unanimity: The absence of any dissenter; the variable that turns out to carry the effect, rather than group size.DEFINED IN Conformity
Unbounded label: A label whose distinct values grow with traffic or with entities you do not control, such as a user, session, or request identifier.DEFINED IN Metric cardinality explosion
Uncertainty-of-outcome hypothesis: The proposal that interest in a contest rises with doubt about its result, supported unevenly in practice.DEFINED IN Handicapping
Unconditional lower bound: A limit proved outright, with no reliance on unproven conjectures, achievable only within a restricted model.DEFINED IN The sorting floor
Unconscious selection: Selection exerted by a routine practice, such as harvesting, without any intent to change the species.DEFINED IN Domestication
Undefined behaviour: A construct for which the standard imposes no requirements at all, on any part of the program.DEFINED IN Undefined behaviour
Under-frequency load shedding: Automatic disconnection of blocks of demand at defined frequency thresholds, as a last-resort rebalancing.DEFINED IN Grid balancing
Under-inclusive: Permitting conduct that does raise it.DEFINED IN Bright-line rules
Under-triage: Assigning a lower priority than warranted, the error that directly costs the individual.DEFINED IN Emergency triage
Underdetermination (in vision): The fact that many possible scenes project to the same retinal image, so perception must infer rather than read off.DEFINED IN Visual grouping
Underdog or reversal effect: The contested finding that relatively younger players who survive selection go on to better careers.DEFINED IN Relative age effect
Undissociated acid: The neutral form of a weak acid, which crosses cell membranes and acidifies the cytoplasm from within.DEFINED IN Sourdough stability
Unfalsifiable charge: An accusation for which no possible observation could count as a disproof.DEFINED IN Witch-hunt cascades
UNGEGN: The United Nations Group of Experts on Geographical Names, which coordinates standardisation and advises on the use of exonyms.DEFINED IN Exonyms
Uniform information density: The hypothesis that speakers spread information at a roughly even rate, compressing predictable material and expanding surprising material.DEFINED IN Word length
Uniform ripening: A mutation removing the tomato's dark green shoulder, which also disables the gene building the fruit's chloroplasts.DEFINED IN Supermarket tomato flavour
Uniformity of nature: The assumed principle that unobserved cases resemble observed ones, which induction needs and cannot independently establish.DEFINED IN Problem of induction
Unihemispheric sleep: Sleeping one cerebral hemisphere at a time, found in cetaceans and some birds.DEFINED IN Sleep
Unilineal descent: Group membership traced through one line only, fathers or mothers.DEFINED IN Merged kinship terms
Union filesystem: A driver such as overlayfs that presents a stack of layers as one merged directory tree.DEFINED IN Layers are diffs
Unit cohesion: The capacity of a body of troops to act together on command, distinct from its size or equipment.DEFINED IN Feigned retreat
Unit in the last place (ulp): The gap between one representable number and the next, which widens as magnitude grows.DEFINED IN Floating-point error
Unit of account: The common measure in which prices, debts and accounts are expressed.DEFINED IN Origin of money
Unit of Work: An object that records everything a business operation changed and coordinates writing it all out in one transaction.DEFINED IN Collecting changes before committing them
Unit price: Price expressed per standard quantity, such as per 100g or per litre, so packs of different sizes can be compared.DEFINED IN Unit-price inversion
Unitary household model: The assumption that a household acts as one decision-maker with one budget; contradicted by evidence that who receives income changes what is bought.DEFINED IN Household money pots
Universal hashing: Choosing a hash function at random from a family, so that the expected collision count is bounded for every input rather than for typical ones.DEFINED IN Finding without searching
Universal scalability law: Neil Gunther's extension adding a coordination cost, which can make throughput fall as workers are added.DEFINED IN Vertical and horizontal scaling
Unknown unknown: A failure mode nobody has conceived of, and which therefore has no instrument, threshold, or alert.DEFINED IN Unknown unknowns · Writing down what you could not determine
Unlink: Removing a directory entry pointing at a file, the operation an ordinary delete performs.DEFINED IN File deletion
Unsaturated fat: A fat whose carbon chains contain double bonds, the reactive sites that make cross-linking possible.DEFINED IN Cast-iron seasoning
Unspecified behaviour: A construct with several permitted outcomes, one of which will occur.DEFINED IN Undefined behaviour
Upcasting: Translating events written under an old schema into the current one at replay time.DEFINED IN Event sourcing
Update / insertion / deletion anomaly: A contradiction or loss caused by one row mixing facts about several subjects.DEFINED IN Normalization
Update anomaly: An inconsistency arising when a repeated fact is changed in some copies and not others.DEFINED IN The untidy shape that answers faster
Upset: A result in which the weaker entrant wins, which is an expected product of a noisy process rather than evidence that the ranking was wrong.DEFINED IN Knockout upsets
Uptake: The receiving party's acknowledgement, without which such an act is offered but not completed.DEFINED IN Apology and repair
Upwelling: The rise of deeper, colder water where surface water has been transported away.DEFINED IN Coastal fog belts · Desert latitudes · Ocean productivity
Urban graveyard effect: The historical pattern of cities having death rates above birth rates.DEFINED IN Urban mortality
Use it or lose it: A doctrine under which an unexercised portion of a water right can be forfeited, penalising anyone who diverts less.DEFINED IN Irrigation efficiency paradox
Use-impact curve: The relationship between how much a site is used and how much it is damaged; typically concave, rising fast then flattening.DEFINED IN Honeypot sites
Use-impact relationship: The measured curve linking passes over a surface to loss of vegetation cover, characteristically steep at first and then flat.DEFINED IN Trail braiding
Use-it-or-lose-it rule: The condition on that entitlement, requiring a minimum share of the series to be operated, recalled as eighty per cent.DEFINED IN Airport slot grandfathering
Uti possidetis: The principle that a newly independent state inherits the boundaries of the administrative unit it succeeds.DEFINED IN Borders
Utilisation: The fraction of time a server is busy; the ratio of arrival rate to service rate.DEFINED IN Border queue surges · Single-queue service · The noisy neighbour
Utilisation cliff: The queueing result that waiting time grows towards infinity as utilisation approaches one, so safe load sits well below capacity.DEFINED IN Rate limiting

V

Vadose passage: One cut above the water table by a stream in an air-filled void, typically a narrow canyon.DEFINED IN Cave formation
Valid-from and valid-to: The stamps marking the window during which a version described the entity.DEFINED IN Recording a change without losing the present
Validation set: Examples held back from training, used to check whether the learned pattern generalizes.DEFINED IN How does a neural network learn? · Overfitting
Validity: The impossibility of true premises with a false conclusion.DEFINED IN What makes an argument logically valid? · Wrong with nothing missing
Validity interval: The pair of stamps marking when a version's claims began and ceased to apply.DEFINED IN Point-in-time joins
Value in use versus value in exchange: Smith's distinction between how much good a thing does and what it will trade for.DEFINED IN Paradox of value
Value-added model: An estimate of a teacher's or school's contribution, based on pupils' gains relative to what their prior attainment predicts.DEFINED IN Value-added ranking instability
Van der Waals force: Short-ranged attraction between molecules arising from fluctuating charge distributions.DEFINED IN Adhesion
Vanishing point: Where the line drawn through the eye parallel to a set of parallel lines pierces the picture plane, and so where their images converge.DEFINED IN Linear perspective
Vapour pressure: The pressure exerted by water molecules in the gas phase; drying runs on the difference between the surface's saturation value and the air's actual one.DEFINED IN Evaporative drying · Freezer burn
Vapour pressure deficit: The difference between the water vapour the air could hold at its temperature and what it actually holds; the driving force for transpiration.DEFINED IN Midday stomatal closure
Variance: Error from a model whose fit changes substantially with a different sample of the same size.DEFINED IN Overfitting · Ubiquity of the bell curve
Variance pooling: Combining independent sources of randomness so that individual outcomes cluster nearer the average.DEFINED IN Single-queue service
Variance reduction: Lowering the swing in day-to-day returns without raising the average.DEFINED IN Sharing under scarcity
Variation: Work outside the quoted scope, priced separately once the job is underway.DEFINED IN Quoting a job
Variety mixture (multiline): A stand sown from several genotypes differing in resistance, used to slow an epidemic without abandoning the crop.DEFINED IN Monoculture fragility
Varnish: A transparent resin coating applied over finished paint to saturate the colours and protect the surface; traditionally mastic or dammar.DEFINED IN Varnish removal
Vascular shunt: A bypass vessel that lets blood skip the exchanger, converting a heat-saving limb into a heat-shedding one.DEFINED IN Countercurrent heat exchange
Vasodilation: Widening of blood vessels, increasing blood flow to the tissue they supply.DEFINED IN Blushing
Vasopressin: The hormone instructing the kidney to retain water, released by exertion and nausea as well as by concentrated plasma.DEFINED IN Exercise-associated hyponatremia
Vec2Text: The 2023 method that inverts embeddings by iteratively correcting a hypothesis using the gap between its embedding and the target.DEFINED IN What a list of numbers remembers
Vector navigation: Following an inherited heading for an inherited length of time, as first-year migrants appear to do.DEFINED IN How do birds know where to migrate?
Vegetative cell: A bacterium in its normal growing, dividing form, which ordinary cooking destroys.DEFINED IN Leftover spoilage
Velocity layer: A separately recorded sample of the same drum struck at a different force, used so repeated hits differ in timbre and not merely in volume.DEFINED IN Groove and microtiming
Vendor lock-in: The accumulated cost and difficulty of moving a workload away from a particular supplier.DEFINED IN The price of being able to leave
Vendor-managed inventory: An arrangement in which the supplier sees the customer's stock levels and decides replenishment, collapsing two forecasts into one.DEFINED IN Bullwhip effect
Vendoring / shading: Bundling or renaming a private copy of a dependency so it cannot collide with another consumer's copy.DEFINED IN Dependency conflicts
Ventral stream: The pathway along the underside of the temporal lobe supporting object and face recognition.DEFINED IN Face recognition
Verbatim transcript: A record of what was uttered including disfluencies, as distinct from the cleaned transcripts used in courts and journalism.DEFINED IN Transcribed speech
Verbatim transcription: Recording a speaker's exact words rather than a restatement of them.DEFINED IN Note-taking by hand
Vernalization: Acquiring competence to flower through prolonged cold, distinct from the cues that later trigger flowering.DEFINED IN Vernalization
Vertex (extreme point): A feasible point that is not the average of two other feasible points.DEFINED IN Corner solutions
Vertical fiscal imbalance: A structural gap between a level of government's revenue-raising capacity and its spending responsibilities.DEFINED IN Conditional spending grants
Vertical scale: A test scale intended to make a point mean the same amount of learning across ages, which seasonal comparisons depend on and which is model-dependent.DEFINED IN Summer learning loss
Vertical scaling: Increasing the capacity of a single machine (scaling up).DEFINED IN Vertical and horizontal scaling
Vertical slice: An increment that crosses every layer for one capability rather than replacing one layer.DEFINED IN Choosing the first piece to replace
Vertical wind shear: A change of wind with height that tilts the vortex and ventilates its warm core.DEFINED IN Hurricane intensification
Very long baseline interferometry: Correlating independently recorded, atomic-clock-stamped data from stations too far apart to link directly.DEFINED IN Radio interferometry
Vestiarium Scoticum: An 1842 book setting out clan-by-clan tartans, whose claimed ancient manuscript source has never been produced.DEFINED IN Folk craft regionalism
Video deficit: The finding that toddlers learn less from recorded screen material than from equivalent live interaction.DEFINED IN Overheard speech and vocabulary
Vigilance decrement: The well-documented decay of sustained attention on tasks where the signal to be detected is rare.DEFINED IN Rubber-stamped review
Virial theorem: The relation, for a bound system of ideal gas, between its gravitational and thermal energy, implying that losing energy makes it hotter.DEFINED IN Stellar hydrostatic balance
Virtual node: One of many ring positions given to a single physical server, to even out arc sizes and express weighting.DEFINED IN Adding a machine without moving the data
Virulence: The harm a pathogen does to its host, usually measured as case fatality or loss of host fitness.DEFINED IN Virulence and transmission
Visa ballot: An immigration lottery admitting applicants at random, used by researchers as a naturally occurring randomised assignment.DEFINED IN Remittances and the children left behind
Viscoelastic: Behaving partly as a viscous liquid and partly as an elastic solid, with the balance depending on temperature and loading rate.DEFINED IN Road cracking
Viscosity: Resistance to flow; for the upper mantle, around 10^21 pascal-seconds, which sets the thousands-of-years timescale of rebound.DEFINED IN Isostatic rebound
Visibility timeout: The period a claimed message is hidden from other consumers, after which it returns if unacknowledged.DEFINED IN Poison messages · When responsibility transfers
Visual cycle: The chemical loop that carries spent retinal out to the pigment epithelium, restores its shape, and returns it to the photoreceptor.DEFINED IN Dark adaptation
Visual hierarchy: The ordering of elements by prominence, so a viewer takes them in a chosen sequence.DEFINED IN Design restraint
Visual word form area: A left ventral occipitotemporal region that becomes selectively responsive to letter strings with literacy.DEFINED IN Reading acquisition
Viva voce voting: The older practice of declaring one's vote aloud to an official.DEFINED IN Secret ballot
Vocabulary: Practised melodic figures a player can deploy without deliberation when a familiar progression arrives.DEFINED IN Jazz improvisation · Tokenization
Volatiles: The light airborne compounds that carry aroma, and with it most of what we call flavour.DEFINED IN Supermarket tomato flavour
Volatility: How readily a component leaves the liquid for the vapour; ethanol's exceeds water's, which is what depletes the film.DEFINED IN Tears of wine
Voltage drop: John List's term for the shrinkage of an effect between a pilot and its scaled version.DEFINED IN Pilot-to-scale failure
Voltage-gated sodium channel: The membrane protein whose opening generates the nerve impulse, and whose inner vestibule these drugs occupy.DEFINED IN Local anaesthetic failure
Volume fraction: The share of a suspension's volume occupied by solid particles; the single most important variable for this behaviour.DEFINED IN Shear-thickening food pastes
Volumetric heat capacity: How much heat a given volume of a material absorbs per degree of temperature rise.DEFINED IN Thermal conductivity of touch
Vortex shedding: Alternating vortices peeling off either side of a bluff body, applying a periodic across-wind force.DEFINED IN Building sway

W

W and R: The number of replicas that must acknowledge a write and be consulted on a read; the guarantee holds when their sum exceeds the replica count.DEFINED IN Quorums
Waiting-time paradox: The case of the inspection paradox concerned with the interval containing a random arrival.DEFINED IN Inspection paradox
Wake deficit: The reduction in wind speed downstream of a rotor, relative to the undisturbed flow.DEFINED IN Wind farm wake losses
Wake maintenance zone: The few hours before habitual bedtime when the circadian alerting signal peaks and sleep onset is hardest.DEFINED IN Teenage sleep phase
Walking a guest: A hotel's remedy for overselling: paying to accommodate the guest at a comparable property.DEFINED IN Overbooking
War of attrition: A contest whose only move is to hold out longer, where waiting is itself costly.DEFINED IN Drafting in the peloton
War-risk premium: The surcharge marine insurers add for voyages through a region judged dangerous, which functions as a toll on continued traffic.DEFINED IN Maritime chokepoints
Warm instance: An execution environment retained after a request completes so the next can reuse what it built.DEFINED IN Warm reuse leaks
Warm-up period: The interval after an instance starts before its metrics are trusted or it is counted as serving.DEFINED IN Scaling that overshoots
Warp and weft: The lengthwise and crosswise yarn sets of a woven cloth.DEFINED IN Bias-cut cloth
Waste heat: The energy a machine consumes that ends up warming its surroundings, which for aDEFINED IN Cooling a room with a fridge
Wasted vote: Any vote cast for a loser, or cast for a winner beyond the number needed to win.DEFINED IN District boundaries
Water activity: The availability of water to microbes, the quantity that salting and drying reduce; distinct from freezer burn, which is physical relocation rather than microbial control.DEFINED IN Freezer burn
Water activity (aw): The availability of water in a food for microbial and chemical use, from 0 to 1.0, where pure water is 1.0.DEFINED IN Food preservation
Water potential: The free energy of water per unit volume relative to pure free water, in megapascals and normally negative in a plant.DEFINED IN Cohesion-tension sap ascent
Water table: The depth below which soil pores are saturated with groundwater; its rise is what enables capillary salt transport.DEFINED IN Salinization
Water-soluble carbohydrates: The soluble sugar reserves in stem bases and roots that a defoliated plant draws on before its new leaf pays for itself.DEFINED IN Grazing rest period
Water-to-cement ratio: Mixing water divided by cement, by mass; the single strongest predictor of hardened strength.DEFINED IN Cement hardening
Water-vapour pressure gradient: The difference in vapour pressure between wet skin and the air, which sets how fast sweat can evaporate.DEFINED IN Heat acclimatization
Watermark: An assertion flowing through the stream that all events earlier than a given event time are believed to have been seen.DEFINED IN Event time versus arrival time · Late-arriving data
Wave speed (celerity): The speed of a pressure disturbance in the fluid-and-pipe system, reduced below the fluid's own sound speed by pipe elasticity and entrained gas.DEFINED IN Water hammer
Wavefront: A surface of constant phase, such as one pressure crest, travelling outward at the medium's own speed once emitted.DEFINED IN Doppler effect
Wavelength: The length of one wave of light; shorter looks bluer, longer looks redder.DEFINED IN Why is the sky blue?
Wavelength-division multiplexing: Carrying many independent channels on one fibre by giving each its own wavelength.DEFINED IN Guided light in fibre
Weak layer: A stratum of low shear strength that can fail beneath a cohesive slab.DEFINED IN Depth hoar in snowpack
Weak-form review: Review in which the court declares an incompatibility but the legislature keeps the final word.DEFINED IN Judicial review
Weakest-link statistics: Treating a body's strength as the minimum over the flaws it contains, from which the size effect follows.DEFINED IN Fibre strength and flaws
Wear levelling: An SSD controller's practice of spreading writes across physical cells to extend drive life, which decouples logical from physical addresses.DEFINED IN File deletion
Wear-out: A failure mode whose rate genuinely rises with age or use, and the only kind scheduled replacement can pre-empt.DEFINED IN Failure after repair
Wear-out phase: The late phase in which fatigue and erosion make failure increasingly likely.DEFINED IN Warranty timing
Weave and capsize: Two modes of the standard bicycle model; weave is the oscillating wobble at low speed, capsize the slow lean-over at high speed.DEFINED IN Bicycle stability
WebAuthn: The browser API for public-key credentials scoped to a relying party, whose signature covers the connected origin.DEFINED IN Why a code sent to your phone does not stop phishing
Weber fraction: The ratio of that increment to the standard; approximately constant over a sense's middle range.DEFINED IN Just-noticeable difference
Webhook: An unsolicited HTTP request a provider sends to your URL to notify you of an event.DEFINED IN A notification you did not ask for
Weight: An adjustable number controlling the influence of a connection.DEFINED IN How does a neural network learn?
Weight decay: A penalty on the magnitude of a model's weights, added to the training objective.DEFINED IN Grokking in training
Weighted average: The aggregate of subgroup rates, weighted by subgroup sizes, which is where the reversal comes from.DEFINED IN Simpson's paradox
Weighted fair queueing: Serving per-tenant queues in proportion to agreed weights, so none monopolises service.DEFINED IN The noisy neighbour
Wetted area: The hull surface actually in contact with water, which sets skin-friction drag.DEFINED IN Rowing crew scale
Wetting: A liquid spreading over a solid rather than beading up, the precondition for an adhesive to reach molecular contact.DEFINED IN Adhesion
Wetting front: The advancing boundary between wetted and dry soil during irrigation.DEFINED IN Irrigation scheduling depth
Whipple index: A measure of that concentration over a middle adult age span, scaled so 100 is no heaping and 500 is total.DEFINED IN Age heaping
White space: Deliberately unused area in a layout, also called negative space; not necessarily white.DEFINED IN Design restraint
Whiteout: The marker written into an upper layer to hide a file present in a lower one; in overlayfs, a character device with major and minor number zero.DEFINED IN Layers are diffs
Wide event: A single structured record per unit of work, carrying many attributes, kept unaggregated so it can be sliced arbitrarily later.DEFINED IN Unknown unknowns
Wien's displacement law: The rule fixing the wavelength at which a warm body radiates most strongly, inversely with its temperature.DEFINED IN Pit viper infrared sensing · Star colors
Wiggle-matching: Fitting a sequence of known spacing against the curve's shape, turning wiggles into a constraint.DEFINED IN Radiocarbon calibration plateaus
Wind gap: A dry notch through a ridge marking a valley whose river has been diverted away.DEFINED IN River capture
Wind-induced surface heat exchange: The feedback in which stronger surface winds increase evaporation, which strengthens the winds further.DEFINED IN Hurricane intensification
Wind-up: The progressive growth of a spinal neuron's response to repeated noxious input at sufficient rate, dependent on NMDA receptors.DEFINED IN Central sensitization · Habituation versus sensitization
Winner's curse: Where the value is uncertain and common, the tendency for the winner to be whoever most overestimated it.DEFINED IN Auction prices · Benchmark saturation
Winning coalition: Any set of parties whose combined seats meet the threshold needed to sustain a government.DEFINED IN Coalition formation
Winogradsky column: A sealed tube of enriched mud left in the light, in which these bands develop over weeks.DEFINED IN Redox banding in sediment
Withdrawal (diversion): The volume taken out of a river or aquifer, whatever later becomes of it.DEFINED IN Irrigation efficiency paradox
Withdrawal resistance: The axial force needed to pull a fastener out of the wood, distinct from its resistance to being sheared sideways.DEFINED IN Screws in end grain
Within-class grouping: Forming attainment groups inside a single classroom for particular work, with the same teacher and curriculum.DEFINED IN Ability grouping
Withitness: Kounin's term for a teacher's demonstrated awareness of what is happening across the room, communicated before misbehaviour escalates.DEFINED IN Small disruptions in a classroom
Witness: A base whose test result proves the candidate composite.DEFINED IN Compositeness without factors
Work: Force applied along a distance; the quantity a machine can redistribute but never create.DEFINED IN Mechanical advantage
Work capacity above the ceiling: The finite amount of work that can be performed above critical power before the effort must be reduced.DEFINED IN Even pacing
Work hardening: The increase in strength that comes from deforming a metal until its own multiplied dislocations obstruct each other.DEFINED IN Alloy strength
Work in progress (WIP): Items that have been started and not yet finished; the inventory of knowledge work.DEFINED IN Limiting work in progress
Work in progress limit: An explicit cap on how many items may be in flight at once, used to shorten queues.DEFINED IN Where the time actually goes
Work-as-imagined and work-as-done: The safety-science distinction between the job as procedures describe it and the job as it is actually accomplished.DEFINED IN Working to rule
Work-in-progress holding cost: What it costs to have partly finished work sitting still, which on a site includes finance, insurance, weather exposure and delayed handover.DEFINED IN Trade demarcation
Work-to-rule: Industrial action in which employees follow every written procedure exactly, reducing output without breaking any rule.DEFINED IN Working to rule
Worked-example effect: The finding that novices learn more from studying solved problems than from solving equivalent ones.DEFINED IN Expertise reversal
Worker policing: The destruction of worker-laid eggs by other workers, enforcing the queen's monopoly on reproduction from below.DEFINED IN Sterile worker castes
Working capital: The money tied up in stock and unpaid customer invoices, less the credit taken from suppliers.DEFINED IN Profit versus cash
Working set: The pages a process has actually referenced in a recent window of time; Denning's measure of what it needs resident.DEFINED IN Memory thrashing
Worst-case stacking: Adding tolerances arithmetically, guaranteeing that any set of conforming parts assembles.DEFINED IN Tolerance stack-up
Wringing: Pressing lapped gauge blocks together so that they adhere strongly, by a mechanism still debated.DEFINED IN Adhesion
Write amplification: The ratio of physical writes performed to logical writes requested.DEFINED IN Indexing
Write barrier: Runtime code injected on reference stores so a concurrent collector learns about graph changes it would otherwise miss.DEFINED IN Garbage collection pauses
Write skew: Two transactions writing different rows in ways that jointly violate a constraint spanning both.DEFINED IN Isolation levels
Write-ahead log: The durable sequential record a database writes before modifying data pages, used for crash recovery and replication.DEFINED IN Change data capture · Database transactions
Write-back / write-through: Deferring writes to the level below until eviction, versus propagating them immediately.DEFINED IN Caching

X

x-height: The height of lowercase letters without ascenders, a better guide to apparent size than point size.DEFINED IN Legibility
XACML: An OASIS standard for access-control policy that defines these roles and the permit / deny / indeterminate / not-applicable outcomes.DEFINED IN Deciding apart from enforcing
Xenia: The Greek guest-host relationship, held under the protection of Zeus as god of strangers.DEFINED IN Guest-right

Y

Yield management: The practice of varying prices and inventory allocation over time to maximise revenue from a perishable, fixed capacity.DEFINED IN Overbooking
Yoked design: Pairing two subjects so they receive identical stimulation while only one can act to end it, isolating controllability.DEFINED IN Learned helplessness

Z

Zeigarnik effect: The finding that interrupted or unfinished material is recalled more readily than completed material.DEFINED IN Earworms · Unfinished tasks
Zero-shot: The same task attempted from a description with no examples at all.DEFINED IN Few-shot prompting
Zero-shot chain-of-thought: Getting the same effect from an instruction such as "let us think step by step", with no worked examples.DEFINED IN Chain-of-thought
Zipf's law of abbreviation: The cross-linguistic tendency for more frequently used words to be shorter.DEFINED IN Word length
Zoning effect: The change caused by cutting a fixed number of zones in a different place.DEFINED IN Modifiable areal units

É

Étendue: Source area times angular spread; conserved by lenses and mirrors, so optically irreducible.DEFINED IN Laser coherence

Β

β: The ratio of radiation pressure to solar gravity on a grain; a fixed property of the grain, independent of distance.DEFINED IN Zodiacal dust replenishment