All articles starting with V
8,490 articles
Volumetric efficiency
Volumetric efficiency is a performance parameter of four-stroke internal combustion engines that measures how effectively the cylinders fill with intake air, typically 80 to 90 percent for naturally aspirated engines and over 100 percent with turbocharging.
Volumetric flask
A volumetric flask is laboratory glassware with a flat-bottomed body and one calibration mark on a long narrow neck, used to prepare standard solutions of exact concentration.
Volumetric flow rate
Volumetric flow rate, also known as volume flow rate, is the volume of fluid passing through a pipe's cross-section per unit time, equal to area times speed.
Volumetric laser endomicroscopy
Volumetric laser endomicroscopy (VLE) is a balloon-based endoscopic imaging method that uses optical coherence tomography to produce wide-field images of the esophageal wall, mainly to detect dysplasia and Barrett's esophagus.
Volumetric modulated arc therapy
Volumetric modulated arc therapy (VMAT) is a form of intensity-modulated radiation therapy in which the linear accelerator rotates around the patient, delivering treatment in 1 to 3 minutes.
Volumetric weight
Volumetric weight, also called dimensional weight or DIM weight, is a notional package weight calculated from length, width, and height, letting carriers price by occupied space.
Volund
Volund is an eruptive center (volcano) on Jupiter's moon Io at 26.3°N, 173.7°W, named for the Germanic smith of the gods. Voyager 1 saw its 100-km plume in 1979; it stayed active through Galileo and Juno.
Völundarkviða
Völundarkviða, meaning "The Lay of Völundr," is an Old Norse Eddic poem telling how the legendary smith Völundr, mutilated and enslaved by King Níðuðr, takes revenge and escapes by flight.
Voluntarism (philosophy)
Voluntarism is a family of philosophical positions that give the will, rather than reason or intellect, the fundamental role in explaining action, morality, metaphysics, or belief.
Voluntary association
Voluntary association: a group people join by choice to pursue shared interests, also called a normative organization in Etzioni's typology. Covers Tocqueville's account, legal meaning, social capital research, and modern sector statistics.
Voluntary carbon market
The voluntary carbon market is a market where companies and individuals voluntarily buy carbon credits, each typically representing one ton of CO2 reduced or removed, to offset emissions.
Voluntary childlessness
Voluntary childlessness, also called being childfree, is the deliberate choice not to have children despite biological capacity. Traced to the 1972 National Organization for Non-Parents, it has risen with education and contraception, reaching 9-10% of younger Norwegian cohorts.
Voluntary counseling and testing
Voluntary counseling and testing (VCT) is a client-initiated HIV service in which a person chooses, after confidential pre-test counseling, whether to be tested, then receives the result with post-test counseling.
Voluntary euthanasia
Voluntary euthanasia is the ending of a patient's life by a physician at the patient's own voluntary, competent request, typically by administering a lethal drug.
Voluntary Hospitals
Voluntary hospitals are private, not-for-profit, self-governing hospitals that historically dominated UK acute care. They were nationalized by the NHS in 1948, remaining 58% of US community hospitals.
Voluntary Human Extinction Movement
The Voluntary Human Extinction Movement (VHEMT), pronounced "vehement," is an environmental movement urging people to stop reproducing so Earth's biosphere can recover, named by Les Knight in the late 1980s.
Voluntary manslaughter
Voluntary manslaughter, also called nonnegligent manslaughter, is an intentional killing reduced from murder because it occurred in the heat of passion or on legally adequate provocation.
Voluntary natural reserve
Voluntary natural reserve: also Freiwilliges Naturreservat, réserve naturelle volontaire. An area of national interest protected voluntarily by its owner to safeguard wildlife, archeological, and geological sites, without state expropriation.
Voluntary Programs
Voluntary programs are programs in which participation is not required, contrasted with mandatory programs; studied in health payment reform, welfare-to-work, environmental regulation, screening, and disclosure, with selection effects shaping outcomes.
Voluntary repatriation of Korean War POWs
Voluntary repatriation of Korean War POWs was the UN principle that prisoners choose whether to return to Communist control, delaying the 1953 armistice by over a year.
Voluntaryism
Voluntaryism (voluntarism) is a libertarian-derived political philosophy holding that all relations should be by mutual consent or not at all, grounded in the non-aggression principle; revived in 1982 by Watner, Smith, and McElroy, it rejects electoral politics and the State.
Volunteer Army
The Volunteer Army (Добровольческая армия) was an anti-Bolshevik force of the Russian Civil War, founded by General M. V. Alekseev at Novocherkassk in November 1917 around former Imperial officers.
Volunteer computing
Volunteer computing is the use of consumer digital devices for high-throughput scientific computing, pioneered by SETI@home in 1999 and now organized mostly through the BOINC middleware.
Volunteer Fighting Corps
The Volunteer Fighting Corps (Kokumin Giyū Sentōtai) was a planned armed civilian militia of the Empire of Japan, created in 1945 to defend the home islands against Allied invasion.
Volunteering
Volunteering is unpaid, freely chosen work for others, formal or informal; global scale about one billion volunteers (2.4% of global GDP), with research on motivations, barriers, participation trends, and retention.
Volunteers-In-Parks
Volunteers-In-Parks (VIP) is the official volunteer program of the US National Park Service, authorized by the Volunteers in the Parks Act of 1970, with over 100,000 volunteers a year.
Volusia County, Florida
Volusia County, Florida: Atlantic-coast county founded 1854 from Orange County, seat DeLand, population 606,573 (2025 est.), 1,101 sq mi, tourism-driven economy centered on Daytona Beach.
Volusianus
Volusianus (Gaius Vibius Afinius Gallus Veldumnianus Volusianus), Roman emperor 251–253, son and co-Augustus of Trebonianus Gallus; reigned through the Cyprian plague and Gothic and Persian attacks, killed with his father at Interamna in 253.
Volusii
Volusii (gens Volusia, Villa dei Volusii Saturnini): Roman senatorial family and their large villa at Fiano Romano near Lucus Feroniae, 30 km north of Rome; discovered 1961 during Autostrada del Sole works, late Republican with Augustan enlargement, free entry.
Völuspá
Völuspá (Vǫluspá), the Old Norse "seeress's prophecy", is the opening poem of the Poetic Edda in Codex Regius, also preserved in Hauksbók, recounting creation, Ragnarök, and rebirth in fornyrðislag meter.