ISO basic Laitin 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' in the U.S. D'Nealian script style

O (named o /ˈoʊ/, plural oes)^[1] is the fifteent letter an a vowel in the ISO basic Latin alphabet.

Its graphic fairm haes an aa remained fairly constant frae Phoenician times till the day. The name o the Phoenician letter wis ʿeyn, meanin "eye", an indeed its shape oreeginates simply as a drawin o a human ee (possibly inspired bi the correspondin Egyptian hieroglyph, c.f. Proto-Sinaitic script). Its oreeginal soond value wis that o a consonant, probably [ʕ], the soond representit bi the cognate Arabic letter letter ع ʿayn.

The uise o this Phoenician letter for a vowel soond is due tae the early Greek alphabets, which adoptit the letter as O "omicron" tae represent the vowel /o/. The letter wis adoptit wi this value in the Auld Italic alphabets, includin the early Latin alphabet. In Greek, a variation o the fairm later came tae distinguish this lang soond (Omega, meanin "large O") frae the short o (Omicron, meanin "smaa o"). Greek omicron gae rise tae the correspondin Cyrillic letter O an the early Italic letter tae runic runic ᛟ.

Even alphabets constructit "frae scratch", i.e. nae derived frae Semitic, uisually hae seemilar fairms tae represent this soond, e.g.; the creators o the Afaka an Ol Chiki scripts, each inventit in different pairts o the warld in the last century, baith attributit thair vowels for 'O' tae the shape o the mooth when makin this soond.

The letter O is the fowert maist common letter in the Inglis leid. O is maist commonly associatit wi the Open-mid back roondit vowel [ɔ], Mid back roondit vowel [o̞] or close-mid back roondit vowel [o] in mony leids. This fairm is colloquially termed the "lang o" as in boat in Inglis, but it is actually maist eften a diphthong /oʊ/ (realized dialectically onywhaur frae [o] tae [əʊ]). In Inglis thare is a "short O" as in fox, which an aa haes several pronunciations. In maist dialects o Breetish Inglis, it is aither an open-mid back roondit vowel [ɔ] or an open back roondit vowel [ɒ]; in American Inglis, it is maist commonly an unroondit back tae a central vowel [ɑː] tae [a].

Common digraphs include 'oo', which represents aither /uː/, /ʊ/ or /ʌ/; 'oi' which teepically represents the diphthong /ɔɪ/, lik the pronunciation o 'oi' in "boil"; an 'ao', 'oe', an 'ou' which represent a variety o pronunciations dependin on context an etymology.

Ither leids uise O for various values, uisually back vowels which are at least pairtly open. Derived letters sic as Ö an Ø hae been creatit for the alphabets o some leids tae distinguish values that wur nae present in Latin an Greek, parteecularly roondit front vowels.

In the Internaitional Phonetic Alphabet, [o] represents the close-mid back roondit vowel.

• Ο ο : Greek letter Omicron
• О о : Cyrillic letter O
• Օ օ : Armenie letter O
• 0 : deegit zero, which is eften confused wi the letter O
• Ø ø : Latin letter Ø
• ∅ : empty set seembol
• ⌀ : diameter seembol
• ° : degree seembol
• º : masculine ordinal indicator (in Galician, Italian, Portuguese, an Spainyie)

¹ An aa for encodins based on ASCII, includin the DOS, Windows, ISO-8859 an Macintosh faimilies o encodins.

NATO phonetic	Morse code
Oscar	–––

		[[File:Sign language {{{fingerspelling}}}.svg|90px]]
Seegnal banner	Banner semaphore	American manual alphabet (ASL fingerspellin)	Braille dots-135

• Media relatit tae O at Wikimedia Commons
• The dictionar defineetion o O at Wiktionary
• The dictionar defineetion o o at Wiktionary