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This article is about the letter of the alphabet. For other uses, see O (disambiguation).
Writing cursive forms of O

O (named o /ˈ/, plural oes)[1] is the 15th letter and the second-to-last vowel in the modern English alphabet and the ISO basic Latin alphabet.


Its graphic form has remained fairly constant from Phoenician times until today. The name of the Phoenician letter was ʿeyn, meaning "eye", and indeed its shape originates simply as a drawing of a human eye (possibly inspired by the corresponding Egyptian hieroglyph, c.f. Proto-Sinaitic script). Its original sound value was that of a consonant, probably [ʕ], the sound represented by the cognate Arabic letter ع ʿayn.

The use of this Phoenician letter for a vowel sound is due to the early Greek alphabets, which adopted the letter as O "omicron" to represent the vowel /o/. The letter was adopted with this value in the Old Italic alphabets, including the early Latin alphabet. 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"). Greek omicron gave rise to the corresponding Cyrillic letter O and the early Italic letter to runic ᛟ.

Even alphabets that are not derived from Semitic tend to 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.[original research?]

Use in writing systems


The letter ⟨o⟩ is the fourth most common letter in the English alphabet.[2] Like the other English vowel letters, it has associated "long" and "short" pronunciations. The "long" ⟨o⟩ as in boat is actually most often a diphthong // (realized dialectically anywhere from [o] to [əʊ]). In English there is also a "short" ⟨o⟩ as in fox, /ɒ/, which sounds slightly different in different dialects. In most dialects of British English, it is either an open-mid back rounded vowel [ɔ] or an open back rounded vowel [ɒ]; in American English, it is most commonly an unrounded back to a central vowel [ɑ] to [a].

Common digraphs include ⟨oo⟩, which represents either // or /ʊ/; ⟨oi⟩ or ⟨oy⟩, which typically represents the diphthong /ɔɪ/, and ⟨ao⟩, ⟨oe⟩, and ⟨ou⟩ which represent a variety of pronunciations depending on context and etymology.

In other contexts, especially before a letter with a minim, ⟨o⟩ may represent the sound /ʌ/, as in 'son' or 'love'.

In English, the letter ⟨o⟩ in isolation before a noun, usually capitalized, marks the vocative case, as in the titles to O Canada or O Captain! My Captain! or certain verses of the Bible.[3]

Other languages

⟨o⟩ is commonly associated with the open-mid back rounded vowel [ɔ], mid back rounded vowel [o̞] or close-mid back rounded vowel [o] in many languages. 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 for the alphabets of some languages to distinguish values that were not present in Latin and Greek, particularly rounded front vowels.

Other systems

In the International Phonetic Alphabet, ⟨o⟩ represents the close-mid back rounded vowel.

Related characters

Descendants and related characters in the Latin alphabet

Derived signs, symbols and abbreviations

Ancestors and siblings in other alphabets

Computing codes

Character O o
Encodings decimal hex decimal hex decimal hex decimal hex
Unicode 79 U+004F 111 U+006F 65327 U+FF2F 65359 U+FF4F
UTF-8 79 4F 111 6F 239 188 175 EF BC AF 239 189 143 EF BD 8F
Numeric character reference O O o o O O o o
EBCDIC family 214 D6 150 96
ASCII g1 79 4F 111 6F
1 Also for encodings based on ASCII, including the DOS, Windows, ISO-8859 and Macintosh families of encodings.

Other representations

NATO phonetic Morse code
Oscar –––
ICS Oscar.svg Semaphore Oscar.svg ⠕
Signal flag Flag semaphore Braille

See also


  1. ^ "O" Oxford English Dictionary, 2nd edition (1989);Chambers-Happap, "oes" op. cit. Oes is the plural of the name of the letter. The plural of the letter itself is rendered Os, O's, os, o's.
  2. ^ English Letter Frequency
  3. ^ "Quick search: "o lord"". Retrieved 2013-12-05. 

External links

  • Media related to O at Wikimedia Commons
  • The dictionary definition of O at Wiktionary
  • The dictionary definition of o at Wiktionary
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