O (disambiguation)

O is the fifteenth letter of the modern Latin alphabet. O may also refer to: In science:

• Oxygen, an element designated by the chemical symbol O
• Haplogroup O (mtDNA), a human mitochondrial DNA (mtDNA) haplogroup
• Haplogroup O (Y-DNA), a Y-chromosomal DNA haplogroup
• A human blood type
• A bluish classification of stars

In mathematics:

• Orthogonal group, designated with O
• Big O notation, used to describe the asymptotic behavior of a function or algorithm

In arts and entertainment:

• O (album), a 2002 album by Damien Rice
• O (Omarion album), a 2005 album by Omarion
• O (film), a 2001 film starring Josh Hartnett, Mehki Phifer and Julia Stiles
• O, The Oprah Magazine, a magazine founded by Oprah Winfrey
• O (Cirque du Soleil), a show at the Bellagio hotel and casino in Las Vegas, Nevada
• O, a fictional character from the French erotic novel Story of O

Other:

• O (name), a Chinese and Japanese family name
• O (kana), a romanization of the kana (お and オ) in Japanese writing
• /o/, the International Phonetic Alphabet symbol for a close-mid back rounded vowel
• An English word used as an interjection to indicate the vocative case, as in "O ye of little faith!"
• The symbol for a hug in Hugs and Kisses (XOXO)
• 'The third person singular pronoun for all he, she, it in the Turkish language

See also

• The O