519,064 articles
Three-dimensional quantum Hall effect
The three-dimensional quantum Hall effect is a generalization of the quantum Hall effect to bulk 3D crystals, proposed by Bert Halperin in 1987 and first observed in ZrTe₅ in 2019.
Three-dimensional space
Three-dimensional space is the space of everyday physical experience, in which every point is specified by three coordinates (x, y, z) along perpendicular axes, denoted mathematically as R³.
Three-domain system
Three-domain system: Woese, Kandler, and Wheelis's 1990 classification of life into Bacteria, Archaea, and Eukarya, based on ribosomal RNA phylogeny; now contested by the two-domain eocyte tree placing Eukarya within Archaea.
Three-Factor Eating Questionnaire
The Three-Factor Eating Questionnaire (TFEQ), also known as the Eating Inventory, is a 51-item self-report questionnaire measuring cognitive restraint, disinhibition, and hunger, published by Stunkard and Messick in 1985.
Three-fifths Compromise
The Three-fifths Compromise (1787) counted three fifths of each state's enslaved population, also called the federal ratio, for House apportionment and direct taxes under Article I, Section 2; superseded by the Fourteenth Amendment.
Three-Fingered Jack
Three-Fingered Jack, born Jack Mansong, was an escaped Jamaican slave who led a band of runaways in the Blue Mountains until Maroon fighters killed him in January 1781.
Three-legged crow
Three-legged crow: solar mythic bird of East Asia, Chinese sanzuwu (三足烏), Japanese yatagarasu (八咫烏), Korean samjogo (삼족오); sun-dweller in Tian Wen and Huainanzi, guide of Emperor Jimmu, Goguryeo tomb emblem, JFA soccer logo.
Three-level neutral-point-clamped inverter
The three-level neutral-point-clamped (NPC) inverter, introduced by Nabae, Takahashi, and Akagi in Japan in 1981, connects each output phase to the positive rail, negative rail, or neutral point.
Three-nucleon force
A three-nucleon force is a nuclear interaction among three protons or neutrons that acts only when all three are present and cannot be reduced to pairwise forces.
Three-peat
A three-peat is the winning of three consecutive championships by one participant in sports, a term coined by Lakers coach Pat Riley, who trademarked it in 1988.
Three-phase electric power
Three-phase electric power is alternating current carried on three conductors with voltages shifted 120 degrees, delivering constant power and needing no return conductor for balanced loads.
Three-phase fault
A three-phase fault, also called a symmetrical fault, is a short circuit in which all three phase conductors connect together. It is the rarest but most severe power-system fault.
Three-phase inverter
A three-phase inverter is a power-electronic converter that converts DC input into three-phase AC output, used for industrial motor drives, solar and wind generation, and battery storage.
Three-phase partitioning
Three-phase partitioning (TPP) is a non-chromatographic bioseparation, reported by Clive Dennison and Rex Lovrien in 1997, that purifies proteins and enzymes from crude suspensions using ammonium sulfate and t-butanol.
Three-phase traffic theory
Three-phase traffic theory is a theory of freeway traffic flow, introduced by Boris S. Kerner, that classifies traffic into free flow, synchronized flow, and wide moving jams.
Three-phase transformer
A three-phase transformer changes the voltage of three-phase alternating current, built as one unit on a shared core or as a bank of three single-phase transformers.
Three-photon microscopy
Three-photon microscopy (3PM) is a laser-scanning fluorescence technique that excites fluorophores by near-simultaneous absorption of three near-infrared photons, reaching deep structures like the mouse hippocampus beyond two-photon limits.
Three-Point Contest
Three-Point Contest (NBA All-Star Saturday Night shooting event, also Three-Point Shootout), held since 1986; Larry Bird, Craig Hodges, and Damian Lillard share the record of three titles; Lillard won 2026 with 29 points over Devin Booker's 27.
Three-point estimation
Three-point estimation is a project estimating technique that combines optimistic, most likely, and pessimistic estimates of cost or duration, originating with the 1950s PERT method for the Polaris Missile System.
Three-point field goal
Three-point field goal: a basketball shot from behind the three-point arc worth three points. NBA line 23'9" (22' corners), FIBA 6.75 m; first used in the 1945 Hobson scrimmage, ABL 1961, ABA 1967, NBA 1979-80.
Three-point hitch
The three-point hitch, or three-point linkage, is a standardized triangular linkage invented by Harry Ferguson that lets a tractor's hydraulics raise, lower, and set the depth of mounted implements; it remains the worldwide standard.
Three-point lighting
Three-point lighting (key-fill-back) is the standard subject-lighting setup in film, video, and photography: key at ~45 degrees sets exposure, fill softens shadows, back light separates subject from background.
Three-point seatbelt
The three-point seatbelt is an occupant restraint combining lap and diagonal chest straps, perfected by Volvo engineer Nils Bohlin in 1959 and credited with saving over a million lives.
Three-section personnel selection of the Ministry of Personnel
The three-section personnel selection (吏部三铨) was the Tang dynasty's procedure by which the Ministry of Personnel examined and appointed civil officials below the fifth rank.
Three-stage least squares
Three-stage least squares (3SLS) is an econometric estimator for systems of simultaneous equations, combining two-stage least squares with cross-equation error correlations, introduced by Zellner and Theil in 1962.
Three-state logic
Three-state logic, or tri-state logic, names two loosely related ideas in electronics: tri-state gate outputs with a disconnected high-impedance state, and three-valued logic with a third indeterminate truth value.
Three-strikes law
Three-strikes law: habitual-offender sentencing statutes imposing doubled or 25-to-life terms after prior serious or violent felonies; enacted in 24 states and federally, 1993-1995; California's 1994 version (Prop 184, amended by Prop 36 in 2012) was the broadest and most used.
Three-toed sloth
Three-toed sloth (Bradypus), slowest-metabolizing arboreal folivore mammal of Neotropical forests; four to five species including pygmy and maned sloths; algae-fur mutualism, weekly ground defecation, pygmy sloth Critically Endangered.
Three-volley salute
Three-volley salute: rifle honor at military funerals, typically seven riflemen firing three blank volleys before Taps; distinct from the artillery 21-gun salute reserved for presidents and heads of state.
Three-volume novel
Three-volume novel (triple-decker, three-decker): a single novel published in three volumes, the prestige British format from Scott's Kenilworth (1821) at 31s 6d until Mudie's and W. H. Smith's 1894 price ultimatum ended it.