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Omega (capital: Ω, lowercase: ω; Greek Ωμέγα) is the 24th and last letter of the Greek alphabet. In the Greek numeric system, it has a value of 800. The word literally means "great O" (''ō mega'', mega meaning 'great'), as opposed to omicron, which means "little O" (''o mikron'', micron meaning "little").〔(The Greek Alphabet )〕 This name is Byzantine; in Classical Greek, the letter was called ''ō'' (), whereas the omicron was called ''ou'' ().〔Herbert Weir Smyth. ''A Greek Grammar for Colleges''. §1〕 The form of the uppercase letter derives from that of an omicron (Ο) broken up at the side (x16px), with the edges subsequently turned outward (x16px, x16px, x16px).〔Anne Jeffery (1961), ''The local scripts of archaic Greece'', p.37–38.〕 The modern lowercase shape goes back to the uncial form x14px, a form that developed during the 3rd century BC in ancient handwriting on papyrus, from a flattened-out form of the letter (x16px) that had its edges curved even further upward.〔Edward M. Thompson (1912), ''Introduction to Greek and Latin paleography'', Oxford: Clarendon. p.144〕 In phonetic terms, the Ancient Greek Ω is a long open-mid ''o'' , comparable to the vowel of British English ''raw''. In Modern Greek, Ω represents the same sound as omicron. The letter omega is transcribed ''ō'' or simply ''o''. In addition to the Greek alphabet, Omega was also adopted into the early Cyrillic alphabet. See Cyrillic omega ((unicode:Ѡ), (unicode:ѡ)). A Raetic variant is conjectured to be at the origin or parallel evolution of the Elder Futhark ᛟ. Omega was also adopted into the Latin alphabet, as a letter of the 1982 revision to the African reference alphabet. It has had little use. See Latin omega. As the last letter of the Greek alphabet, Omega is often used to denote the last, the end, or the ultimate limit of a set, in contrast to alpha, the first letter of the Greek alphabet. Omega is also used in Christianity, as a part of the Alpha and Omega metaphor. == The symbol Ω (uppercase letter) == The uppercase letter Ω is used as a symbol: * In chemistry: * * For oxygen-18, a natural, stable isotope of oxygen.〔http://www.cedex.es/NR/rdonlyres/B8A9522A-5D6F-4675-921A-24BB8458187B/124720/Capilla_et_al_geoENV_2012_Valencia_Espa%C3%B1a_Extended.pdf〕 * In physics: * * For ohm – SI unit of electrical resistance; formerly also used upside down ((unicode:℧)) to represent mho, the old name for the inverse of an ohm (now siemens with symbol S) used for electrical conductance. Unicode has a separate code point for the ohm sign (U+2126, Ω), but it is included only for backward compatibility, and the Greek uppercase omega character (U+03A9, Ω) is preferred.〔Excerpts from ''(The Unicode Standard, Version 4.0 )''. Retrieved 11 October 2006.〕 * * In statistical mechanics, Ω refers to the multiplicity (number of microstates) in a system. * * The solid angle or the rate of precession in a gyroscope. * * In particle physics to represent the Omega baryons. * * In astronomy (cosmology), Ω refers to the density of the universe, also called the density parameter. * * In astronomy (orbital mechanics), Ω refers to the longitude of the ascending node of an orbit. *In mathematics and computer science: * * In complex analysis, the Omega constant, a solution of Lambert's W function * * A variable for a 2-dimensional region in calculus, usually corresponding to the domain of a double integral. * * In topos theory, the (codomain of the) subobject classifier of an elementary topos. * * In combinatory logic, the looping combinator, ''(λ x. x x) (λ x. x x)'' * * In group theory, the omega and agemo subgroups of a ''p''-group, Ω(''G'') and ℧(''G'') * * In group theory, Cayley's Ω process as a partial differential operator. * * In statistics, it is used as the symbol for the sample space, or total set of possible outcomes. * * In number theory, Ω(''n'') is the number of prime divisors of ''n''. * * In notation related to Big O notation to describe the asymptotic behavior of functions. * * Chaitin's constant. *As part of logo or trademark: * * The logo of Omega Watches SA. * * Part of the Badge of the Supreme Court of the United Kingdom. * * Part of the mission patch for STS-135, as it was the last mission of the Space Shuttle program. * * The logo of the God of War video game series based on Greek mythology. * * The logo of E-123 Omega, a ''Sonic the Hedgehog'' character. * * The logo of the Heroes of Olympus series, based on Greek mythology. * * the logo of the Ultramarines in Warhammer 40,000 * * The logo of Primal Groudon, the version mascot of ''Pokémon Omega Ruby''. *Other * * The symbol of the resistance movement against the Vietnam-era draft * * Year or date of death * * Used to refer to the lowest-ranked wolf in a pack * * In eschatology, the symbol for the end of everything * *In molecular biology, the symbol is used as shorthand to signify a genetic construct introduced by a two-point crossover 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Omega」の詳細全文を読む スポンサード リンク
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