All articles starting with F
15,892 articles
Four-letter word
Four-letter word: English idiom for a short taboo swear word, typically referring to sex or excrement (fuck, shit, cunt); phrase attested from the 1920s, popularized by Cole Porter's 1934 Anything Goes, and extended jokingly to any disliked thing.
Four-level pulse-amplitude modulation
Four-level pulse-amplitude modulation (PAM4, also written PAM-4) encodes two bits per symbol using four amplitude levels, doubling throughput over NRZ at the same symbol rate.
Four-minute mile
Four-minute mile: running 1,609.04 m under 4:00, first achieved by Roger Bannister (3:59.4, Oxford, 6 May 1954). Over 1,000 men have since done it; men's record now Josh Kerr's 3:42.66, women's record Faith Kipyegon's 4:07.64.
Four-momentum
The four-momentum, or energy-momentum 4-vector, is the four-vector in special relativity that combines a particle's energy and momentum, with rest mass as its invariant length.
Four-point bending test
The four-point bending test measures flexural strength and modulus by loading a simply supported beam at two inner points, where bending moment is constant and shear is zero.
Four-point contact ball bearing
A four-point contact ball bearing is an angular contact bearing with gothic arch raceways giving four contact points per ball, replacing a matched pair of bearings in half the axial space.
Four-qubit silicon quantum processor
The four-qubit silicon quantum processor, built by Sydney company Silicon Quantum Computing under Michelle Simmons, uses phosphorus atoms in pure silicon and ran Grover's algorithm at 98.9% fidelity in February 2025.
Four-room house
The four-room house is a domestic building type of the Iron Age southern Levant, from about 1200 to 586 BC, with three long spaces and a broad back room.
Four-seam fastball
Four-seam fastball (FF): baseball's fastest, straightest, most-used pitch, gripped across the seams with backspin. MLB average about 94 mph, roughly 2,260 rpm spin, 31.8% of 2024 pitches.
Four-step travel demand model
The four-step travel demand model (FSM) is an aggregate, trip-based forecasting procedure that estimates regional travel in four sequential stages, from trip generation through network assignment.
Four-stroke engine
A four-stroke engine is an internal combustion engine that completes one power cycle in four piston strokes, intake, compression, power, and exhaust, invented by Nicolaus Otto in 1876.
Four-terminal sensing
Four-terminal sensing, also called Kelvin sensing or four-wire measurement, is an electrical technique that measures resistance accurately by using separate pairs of current-carrying and voltage-sensing leads.
Four-vector
A four-vector, also called a Lorentz vector, is a set of four quantities transforming like spacetime event coordinates under Lorentz transformations, the basic objects of Minkowski space in special relativity.
Four-velocity
The four-velocity is the derivative of a particle's spacetime position with respect to its proper time, written Uμ = dxμ/dτ, making it a Lorentz four-vector.
Four-wave mixing
Four-wave mixing, also called four-photon mixing, is a nonlinear optical process in which two or three light waves at different wavelengths generate new waves at other wavelengths.
Four-way reversing valve
A four-way reversing valve is a four-port valve in a heat pump's refrigerant circuit that reverses refrigerant flow, letting one system heat and cool a space.
Four-wheel drive
Four-wheel drive, also known as four by four or 4x4, is a drivetrain that sends engine or motor torque to all four wheels of a vehicle via a transfer case.
Four-wheel steering
Four-wheel steering (4WS) steers a vehicle's rear wheels as well as its fronts, for stability at high speed and a tighter turning radius at low speed.
Four-Year Plan (Poland)
The Four-Year Plan (Czteroletni Plan Inwestycyjny) was a Polish state investment program running from 1936 to 1940, prepared by Eugeniusz Kwiatkowski to lift Poland out of the Great Depression.
Four-zhu coin
The four-zhu coin (四铢钱) was a copper coin cast by the Liu Song dynasty in 430, the Southern dynasties' first coinage, later re-cast in 454 bearing the Xiaojian era title.
Four: A Divergent Collection
Four: A Divergent Collection (2014, HarperCollins) is Veronica Roth's companion volume of four pre-Divergent stories plus three Divergent scenes, narrated by Tobias Eaton, the trilogy's Dauntless instructor Four.
Fourah Bay College
Fourah Bay College (FBC), founded 18 February 1827 by the Church Missionary Society, is the oldest constituent college of the University of Sierra Leone on Mount Aureol, Freetown; first Western-style university in West Africa, Durham-affiliated from 1876, seven faculties, bicentennial in 2027.
Fourdrinier machine
The Fourdrinier machine is a papermaking machine that forms a continuous web of paper on a moving wire screen, patented in 1807 and named for Henry and Sealy Fourdrinier.
Fourever You
Fourever You (เพราะรักนำทาง), also Fo(u)rever You Project, is a Thai BL university romance by Studio Wabi Sabi on GMM25 and WeTV, airing 2024–2026 in two seasons adapted from Howlsairy novels.
Fourever You 2 (เดือนว่านี่น่ารัก)
Fourever You 2 (เพราะรักนำทาง พาร์ท 2), aka Fourever You Season 2 or Part 2, is a 2025–2026 Thai BL university romance anthology by Studio Wabi Sabi on GMM25 and WeTV, with three eight-episode arcs adapted from Howlsairy novels.
FourFiveSeconds
FourFiveSeconds: 2015 acoustic folk-pop single by Rihanna with Kanye West and Paul McCartney, released January 24, 2015, peaked at No. 4, in D major, later excluded from the album Anti.
Fourfold division of the Sasanian army
The fourfold division of the Sasanian army was a sixth-century reform by Khosrow I replacing the single army commander with four generals, one per quarter of the realm.
Fourier analysis
Fourier analysis, also called Fourier theory, is the branch of mathematics that expresses functions as sums of sines and cosines, founded by Joseph Fourier's 1807 work on heat conduction.
Fourier Intelligence (傅利叶智能)
Fourier Intelligence (傅利叶智能) is a Shanghai robotics company founded in 2015 by Gu Jie and Xu Zhenhua, known for rehabilitation robots and the GR series of humanoid robots.
Fourier multiplier
A Fourier multiplier is a linear operator acting on a function by multiplying its Fourier transform by a fixed symbol and transforming back, equivalently convolution with a kernel.