The letter O is the fifteenth letter in the Latin alphabet. Its name in English is o , plural o's or oes (both pronounced ).

History

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Egyptian hieroglyph `ir	Proto-Semitic O	Phoenician O	Etruscan O	Greek Omicron	-	D4

The letter was derived from the Semitic `Ayin (eye), which represented a consonant, probably the pharyngeal consonant (IPA ) pronounced similar to the Arabic letter ع called `Ayn. This Semitic letter in its original form seems to have been inspired by a similar Egyptian hieroglyph for "eye".

The Greeks are thought to have come up with the innovation of vowels, and lacking a pharyngeal consonant, employed this letter as the Greek (O) to represent the vowel /o/, a sound it maintained in Etruscan and Latin. In Greek, a variation of the form later came to distinguish this long sound (Omega, meaning "large O") from the short o (Omicron, meaning "small o").

Its graphic form has also remained fairly constant from Phoenician times until today. Indeed, even alphabets constructed "from scratch", ie not derived from Semitic, usually have similar forms to represent this sound -- for example the creators of the Afaka and Ol Chiki scripts, each invented in different parts of the world in the last century, both attributed their vowels for 'O' to the shape of the mouth when making this sound.

Usage

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O is most commonly associated with the . In English, though, O has a short value which maps to ( in parts of North America), while the long value tends to a diphthong of and . Common digraphs include OO (inconsistently with the sound or ), OI (usually a diphthong of and ), as well as OA, OE, and OU with a variety of pronunciations depending on context.

Other languages use O for various values, usually back vowels which are at least partly open. Derived letters such as Ö and Ø have been created by some languages to distinguish values that were not present in Latin and Greek, particularly rounded front vowels.

In the International Phonetic Alphabet, ^* represents the close-mid back rounded vowel.

Codes for computing

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In Unicode the capital O is codepoint U+004F and the lowercase o is U+006F.

The ASCII code for capital O is 79 and for lowercase o is 111; or in binary 01001111 and 01101111, correspondingly.

The EBCDIC code for capital O is 214 and for lowercase o is 150.

The numeric character references in HTML and XML are "O" and "o" for upper and lower case respectively.

Distinguishing O from zero

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See 0: Distinguishing zero from O

Meanings for O

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• O is a word in English, used as an interjection to indicate the vocative case, as in "O ye of little faith!"
• In astronomy,
  • O stands for a July 16 through 31 discovery, in the provisional designation of a comet (e.g. C/1995 O1, Comet Hale-Bopp) or asteroid (e.g. (4878) 1968 OF).
• In chemistry, O stands for oxygen.
• In economics, O usually represents output.
• In mathematics, O designates orthogonal groups.
• In medicine, O (also, O+ or O-) is one of the human blood types.
• In Microsoft Windows, Ctrl + O, and Mac OS, Command-O, opens a file.
• In Normandy, O is a well-known and picturesque château. See Château d'O.
• O is a symbol for a hug, as in love notes. (See Hugs and Kisses.)
• O is the nickname of a magazine founded by Oprah Winfrey, more formally called O, The Oprah Magazine.
• O may refer to the 2002 album by Damien Rice, see O (album).
• O is a black metal music band, see O (band).
• O is the third person singular pronoun for all he, she, it in Turkish.
• O is a film, see O (film).
• Ō is a family name in Japanese; see O (name).
• O is a Chinese family name, represented by 柯; see O (name).
• Story of O is a French erotic novel.
• O is the name of a production show by Cirque du Soleil at the Bellagio in Las Vegas.
• Big O notation is, in mathematics and computer science, used to describe the asymptotic behavior of a function or algorithm.
• o for ordentlich in German, meaning "of order". This was a title given to Austrian university professors of tenure status that are also research heads in their department. It was abolished in 1997, however, those who received it prior to its abandonment are allowed to continue using it. The "o" is placed before the rest of the professor's title.
• "O" was a minor character in the Transformers comics.

See also

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Latin_letters | Vowel letters

O | O | O | O | O | O | O | O | O | O | O | O | O | O | O | O | O | O | O | O | O | O (letter) | O | O | O | O | O | O | O | O | O | O | O | O | O | O