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For other uses, see Omega (disambiguation).
Omega (Ω ω) 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').[1] This name is Byzantine; in Classical Greek, the letter was called ō (ὦ), whereas the Omicron was called ou (οὖ).[2]
The form of the letter derives from a double omicron, which came to be written open at the top.
Phonetically, the Ancient Greek Ω is a long o, similar to the vowel of English close. It is transcribed ō or simply o. In Modern Greek Ω is a short o similar to the vowel of British English pot.
The Omega symbol is now to be represented as one on the six numbers that formulate the universe founded by Martin J. Rees.The cosmic number omega measures the amount of material in our Universe - galaxies, diffuse gas, and 'dark matter'. Omega tells us the relative importance of gravity and expansion energy in the Universe. A universe within which omega was too high would have collapsed long ago; had omega been too low, no galaxies would have formed. The inflationary theory of the Big Bang says omega should be one; astronomers have yet to measure its exact value.[citation needed]
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. In the Bible, God declares himself to be the "Alpha and Omega, the beginning and the end, the first and the last".[3]
Omega was also adopted into the early Cyrillic alphabet. See omega (Cyrillic) (Ѡ, ѡ). A Raetic variant is at the origin of Elder Futhark ᛟ.
[edit] The symbol Ω (upper case letter)
The upper-case letter Ω is used as a symbol, it is also used often outside its Greek alphabetical context in literature, advertising and other forms of human expression.
- For ohm — SI unit of electrical resistance; formerly also used upside down (℧) 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 only included for backwards compatibility and the Greek uppercase omega character (U+03A9, Ω) is preferred.[4]
- In computer science, in notation related to Big O notation to describe the asymptotic behavior of functions. See also Chaitin's constant
- In mathematics, the Omega constant, a solution of Lambert's W function; or the first uncountable ordinal number (also known as ω1)
- In physics, the solid angle.
- In particle physics to represent the Omega baryons. A lowercase omega is used for the omega mesons.
- In combinatory logic, the looping combinator, (λ x. x x) (λ x. x x)
- In astronomy (cosmology) Ω refers to the density of the universe, also called the density parameter.
- In automobiles, the 1983 Oldsmobile Omega.
[edit] The symbol ω (lower-case letter)
The lower-case letter ω is used as a symbol:
- In textual criticism, the archetype of a manuscript tradition
- In physics, angular velocity and angular frequency.
- In mathematics, the first transfinite ordinal number
- In number theory, an arithmetic function
- In combinatory logic, the self-application combinator, (λ x. x x)
- In computer science, in notation related to Big O notation, the asymptotically dominant nature of functions
- In astronomy, as a ranking of a star's brightness
- In particle physics to represent the omega meson
- In circuit analysis and signal processing to represent angular velocity, related to frequency f by ω = 2πf.
- In biochemistry to denote the carbon atom furthest from the carboxyl group of a fatty acid.
- Used in place of ん in Japanese typing shorthand.
