Omicron

This article is about the Greek letter Ο. For the genus of the same name, see Omicron (genus). For video game, see Omikron: The Nomad Soul.

Greek alphabet
Αα	Alpha	Νν	Nu
Ββ	Beta	Ξξ	Xi
Γγ	Gamma	Οο	Omicron
Δδ	Delta	Ππ	Pi
Εε	Epsilon	Ρρ	Rho
Ζζ	Zeta	Σσς	Sigma
Ηη	Eta	Ττ	Tau
Θθ	Theta	Υυ	Upsilon
Ιι	Iota	Φφ	Phi
Κκ	Kappa	Χχ	Chi
Λλ	Lambda	Ψψ	Psi
Μμ	Mu	Ωω	Omega
History
Archaic local variants  ·  ·  ·  ·  ·
Ligatures (ϛ, ȣ, ϗ) · Diacritics
Numerals: (6) · (90) · (900)
In other languages
Bactrian  · Coptic  · Albanian
Scientific symbols
Book  · Category · Commons

Omicron (uppercase Ο, lowercase ο, literally "small o": Όμικρον, o mikron, micron meaning 'small' in contrast to omega) is the 15th letter of the Greek alphabet. In the system of Greek numerals it has a value of 70. It is rarely used in mathematics because it is indistinguishable from the Latin letters O, o and easily confused with the digit 0. This letter is derived from the Phoenician letter Ayin. In modern Greek, omicron represents the sound [ɔ]. Letters that arose from omicron include Roman O and Cyrillic O.

In Unicode the capital letter is codepoint U+039F and the lowercase is U+03BF.

The upper-case letter of omicron (O) was originally used in mathematics as a symbol for Big O notation, representing the asymptotic rate of growth of a function.

In popular culture

• Omicron is frequently used to designate the thirteenth star in a constellation group, using a combination of magnitude and position. Stars with the omicron designation include Omicron Andromedae, Omicron Ceti, and Omicron Persei. The last of these is well-known due to its use as a setting in science fiction, including Star Trek, Mystery Science Theater 3000, Transformers, and Futurama.