O

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

ISO basic Latin alphabet Aa Bb Cc Dd Ee Ff Gg Hh Ii Jj Kk Ll Mm Nn Oo Pp Qq Rr Ss Tt Uu Vv Ww Xx Yy Zz

Cursive script 'o' and capital 'O'

O (named o /ˈoʊ/, plural oes) is the fifteenth letter and a vowel in the ISO basic Latin alphabet.

History

Its graphic form has also 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 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 runic ᛟ.

Even alphabets constructed "from scratch", i.e. not derived from Semitic, usually have similar forms to represent this sound, e.g.; 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

The letter O is the fourth most common letter in the English language. O is most 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. This form is colloquially termed the "long o" as in boat in English, but it is actually most often a diphthong /oʊ/ (realized dialectically anywhere from [o] to [əʊ]). In English there is a "short O" as in fox, which also has several pronunciations. 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 [ɑː] to [a].

Common digraphs include 'oo', which represents either /uː/, /ʊ/ or /ʌ/; 'oi' which typically represents the diphthong /ɔɪ/, like the pronunciation of 'oi' in "boil"; and 'ao', 'oe', and 'ou' which represent a variety of pronunciations depending on context and etymology.

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.

In the International Phonetic Alphabet, [o] represents the close-mid back rounded vowel.

Related letters and other similar characters

• Ο ο : Greek letter Omicron
• О о : Cyrillic letter O
• Օ օ : Armenian letter O
• 0 : digit zero, which is often confused with the letter O
• Ø ø : Latin letter Ø
• ∅ : empty set symbol
• ⌀ : diameter symbol
• ° : degree symbol
• º : masculine ordinal indicator (in Galician, Italian, Portuguese, and Spanish)

Computing codes

Character	O		o
Unicode name	LATIN CAPITAL LETTER O		LATIN SMALL LETTER O
Encodings	decimal	hex	decimal	hex
Unicode	79	U+004F	111	U+006F
UTF-8	79	4F	111	6F
Numeric character reference	O	O	o	o
EBCDIC family	214	D6	150	96
ASCII 1	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	–––

Signal flag	Flag semaphore	Braille

External links

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

The ISO basic Latin alphabet
Aa	Bb	Cc	Dd	Ee	Ff	Gg	Hh	Ii	Jj	Kk	Ll	Mm	Nn	Oo	Pp	Qq	Rr	Ss	Tt	Uu	Vv	Ww	Xx	Yy	Zz
Letter O with diacritics
Óó	Òò	Ŏŏ	Ôô	Ốố	Ồồ	Ỗỗ	Ổổ	Ǒǒ	Öö	Ȫȫ	Őő	Õõ	Ṍṍ	Ṏṏ	Ȭȭ	Ȯȯ	O͘o͘	Ȱȱ	Øø	Ǿǿ	Ǫǫ	Ǭǭ	Ōō	Ṓṓ	Ṑṑ
Ỏỏ	Ȍȍ	Ȏȏ	Ơơ	Ớớ	Ờờ	Ỡỡ	Ởở	Ợợ	Ọọ	Ộộ	Ɵɵ	Ɔɔ	ⱺ
Related
Derivations Diacritics History ISO/IEC 646 List of letters Numerals Palaeography Punctuation Unicode