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Discrete valuation ring
A discrete valuation ring (DVR) is a principal ideal domain with exactly one nonzero prime ideal; examples include the power series ring k[[t]] and the integers localized at a prime.
Discrete wavelet transform
The discrete wavelet transform (DWT) is a linear transform that decomposes a discrete signal into wavelet coefficients carrying both scale and position information, computed by a fast filter-bank algorithm.
Discrete-time Fourier transform
The discrete-time Fourier transform (DTFT) maps a discrete-time sequence to a continuous, periodic function of frequency; the DFT samples it at finitely many frequencies, computed efficiently by the FFT.
Discretionary fiscal policy
Discretionary fiscal policy is the deliberate change of government spending or tax law by a legislature to influence aggregate demand, as distinct from automatic stabilizers.
Discretization
Discretization, also called discretizing, replaces a continuous mathematical problem with a finite discrete counterpart a computer can solve, turning differential equations into algebraic systems and signals into samples.
Discriminant
The discriminant is a quantity computed from the coefficients of a polynomial or quadratic form that vanishes exactly when the object degenerates, as when two roots coincide.
Discriminant analysis
Discriminant analysis is a family of supervised statistical classification methods that model differences between known groups and assign new observations to the group they most likely belong to.
Discrimination
Discrimination is unjust treatment based on race, sex, religion, disability, or origin, spanning direct, indirect, and structural forms. Covered via UN treaties, EEOC employment law, field-experiment evidence, and global prevalence data.
Discrimination against atheists
Discrimination against atheists, also called persecution of atheists, is the legal exclusion, stigma, and distrust directed at people who do not believe in a god.
Discrimination against autistic people
Discrimination against autistic people, also called persecution of people with autism, is unfavorable treatment in employment, education, healthcare, and criminal justice, with documented employment gaps and hate crime.
Discrimination against Otaku (オタク差別)
Discrimination against otaku (オタク差別) is stigma toward anime, manga, and game fans: coined derogatorily in 1983, intensified by the 1989 Miyazaki murder moral panic, partially eased by mainstreaming since the late 2000s.
Discrimination testing
Discrimination testing is a family of sensory evaluation methods that tests whether people can perceive a difference between two products, using forced-choice formats like the triangle test.
Discriminative model
A discriminative model is a machine learning model that learns a direct mapping from input features to output labels, the conditional probability p(y|x), with examples like logistic regression, support vector machines, and neural network classifiers.
Discus (fish)
Discus (Symphysodon) are disc-shaped Amazonian cichlid aquarium fish, the "King of Aquarium Fishes," known for biparental mucus feeding of fry, about 100 color strains, $60–80 retail prices, and IUCN Least Concern status despite heavy ornamental trade.
Discus throw
Discus throw: Olympic track and field event throwing a disc from a 2.5 m circle. Ancient pentathlon event, modern since 1896. Men's WR 75.56 m (Alekna, 2025); women's WR 76.80 m (Reinsch, 1988).
Discusión
Discusión is a collection of essays by Argentine writer Jorge Luis Borges, first published in Buenos Aires in 1932 and expanded in 1957 as volume six of his Obras completas.
Discworld
Discworld is Terry Pratchett's 41-novel comic fantasy series (1983-2015), set on a flat world carried by four elephants on a giant star turtle, featuring Death, Granny Weatherwax, and Sam Vimes of Ankh-Morpork.
Discworld (video game)
Discworld (1995) is a point-and-click adventure by Teeny Weeny Games and Perfect 10 Productions, published by Psygnosis, starring Eric Idle-voiced Rincewind in an original dragon plot for Ankh-Morpork, released on DOS, Mac, PlayStation, and Saturn.
Discworld (world)
Discworld is Terry Pratchett's fictional flat world carried by four elephants on the star turtle Great A'Tuin, setting of 41 satirical fantasy novels (1983-2015) run on magic and narrativium.
Discworld II: Missing Presumed...!?
Discworld II: Missing Presumed...!? (US title Mortality Bytes!) is a 1996 Perfect Entertainment point-and-click adventure published by Psygnosis, in which Rincewind must find the missing Death; released on DOS, Windows, PlayStation, and Saturn.
Discworld Noir
Discworld Noir is a 1999 point-and-click adventure by Perfect Entertainment and GT Interactive, the third Discworld game, starring private investigator Lewton with a notebook-based clue system; released only in Europe, never in North America.
Disdrometer
A disdrometer, also called a distrometer, is an instrument that measures the drop size distribution and fall velocity of precipitation particles reaching the ground, used to calibrate weather radar.
Disdyakis triacontahedron
The disdyakis triacontahedron, also called the hexakis icosahedron, is a Catalan solid with 120 scalene triangular faces, the most of any Catalan solid, and serves as the shape of the 120-sided die.
Disease
A disease is a condition in which bodily structures or functions deviate from the norm, typically with characteristic signs and symptoms, classified internationally by the WHO's ICD since 1893.
Disease (Lady Gaga song)
Disease is a 2024 Lady Gaga song released October 25, 2024 on Interscope as lead single of Mayhem (LG7); dark industrial dance-pop written with Polansky, Watt, and Cirkut, peaking at number 7 in the UK.
Disease activity measures and treat-to-target in rheumatoid arthritis
Disease activity measures in rheumatoid arthritis, including DAS28, CDAI, SDAI, and Boolean criteria, guide treat-to-target: adjusting therapy until remission or low disease activity is reached.
Disease activity score
The disease activity score (DAS) is a composite clinical index for rheumatoid arthritis that combines joint counts, patient global assessment, and ESR or CRP to guide treatment.
Disease Management
Disease management, also called disease state management or chronic disease management, is coordinated healthcare for chronic conditions using guidelines, self-management support, and multidisciplinary teams; originated in 1990s US managed care, now evolved into population health management.
Disease management in bivalve aquaculture
Disease management in bivalve aquaculture is the set of surveillance, regulatory, biosecurity, and breeding practices used to prevent, detect, and limit infectious disease in farmed oysters, mussels, and clams.
Disease mapping
Disease mapping is the set of statistical methods for estimating and displaying how disease risk varies across small geographic areas, typically by smoothing unstable local rates.