O is the fifteenth letter of the modern Latin alphabet.
O may also refer to:
Օ, a letter in the Armenian alphabet
O (Cyrillic), a letter of the Cyrillic alphabet
O (kana), a romanization of the kana (お and オ) in Japanese writing
ㅇ, a consonant in Hangul, the Korean alphabet
ဝ, a consonant in Burmese script
/o/, the International Phonetic Alphabet symbol for a close-mid back rounded vowel
O, an IRC operators service in QuakeNet's IRC services
O, chemical symbol for oxygen
O, a human blood type, the universal donor
Haplogroup O (Y-DNA), a Y-chromosomal DNA haplogroup
O, for pyrrolysine an alpha amino acid in biochemistry
Class O, stellar classification for very hot bluish stars
O word, an antiquated vocative placed before a name of, or phrase characterizing, the party being addressed in speech
O (also P), the patient-like argument (object) of a canonical transitive verb
Big O notation, used to describe the asymptotic behavior of a function or algorithm
O, for orthogonal group
o indicates function composition or composition of morphisms in a category
O
, a category of Lie algebra representations
o, for octet, an information measure unit used in computing
O (surname), Korean and Japanese surnames romanized "O" or "Oh"
Ou (surname), Chinese and Cantonese surnames pronounced "O" or "Oh"
A prefix meaning "grandson (of)", appearing in Irish surnames
Genovevo de la O (1876-1952) - Mexican revolutionary
Karen O, born Karen Lee Orzolek, American singer
O Brook, a short river in Devon, England
Essie's Original Hot Dog shop (commonly known as "The O"), a restaurant in Pittsburgh, Pennsylvania
Arts and entertainment
Films and television
O (film), 2001 film starring Josh Hartnett, Mekhi Phifer and Julia Stiles
Literature
O: A Presidential Novel, anonymous novel published in 2011
O, fictional planet that is the setting of several short stories by science fiction author Ursula K. Le Guin
O, fictional character from the French erotic novel Story of O
Media and publications
O, The Oprah Magazine, magazine founded by Oprah Winfrey
«O», an international fetish magazine
Music
O (Damien Rice album), 2002
O (Eiko Shimamiya album), 2006
O (Omarion album), 2005
"O" (Omarion song), the title song
o (Tilly and the Wall album), 2008
O, 2002 album by Zone
"O" (Coldplay song), 2014
"o", a song by iamamiwhoami
Sports
O (gesture), a gesture used to show support for the sports teams of the University of Oregon
Others
O (Cirque du Soleil), show at the Bellagio hotel and casino in Las Vegas, Nevada
O-class battlecruiser, class of German ships in the 1930s
The O (political group) (The Organization), a 1970s American political group
O (disambiguation) Wikipedia (Text) CC BY-SA