Cyrillic letter O
Phonetic usage:	[o], [ɔ], [ɐ], [ɒ], [ʌ]
Numeric value:	70
Derived from:	Greek letter Omicron (Ο ο)
The Cyrillic script
Slavic letters
А А̀ А̂ А̄ Ӓ Б В Г Ґ Д Ђ Ѓ Е Ѐ Е̄ Е̂ Ё Є Ж З З́ Ѕ И І Ї Ꙇ Ѝ И̂ Ӣ Й Ј К Л Љ М Н Њ О О̀ О̂ Ō Ӧ П Р С С́ Т Ћ Ќ У У̀ У̂ Ӯ Ў Ӱ Ф Х Ц Ч Џ Ш Щ Ꙏ Ъ Ъ̀ Ы Ь Ѣ Э Ю Ю̀ Я Я̀
Non-Slavic letters
Ӑ А̊ А̃ Ӓ̄ Ӕ Ә Ә́ Ә̃ Ӛ В̌ Ԝ Г̑ Г̇ Г̣ Г̌ Г̂ Г̆ Г̈ г̊ Ҕ Ғ Ӻ Ғ̌ ғ̊ Ӷ Д́ Д̌ Д̈ Д̣ Д̆ Ӗ Е̃ Ё̄ Є̈ Ԑ Ԑ̈ Җ Ӝ Ӂ Ж̣ Ҙ Ӟ З̌ З̣ З̆ Ӡ И̃ Ӥ Ҋ Қ Ӄ Ҡ Ҟ Ҝ К̣ к̊ қ̊ Ԛ ᴫ Л́ Ӆ Ԯ Ԓ Л̈ Ӎ ᵸ Н́ Ӊ Ң Ԩ Ӈ Ҥ О̆ О̃ Ӧ̄ Ө Ө̄ Ө́ Ө̆ Ӫ Ԥ П̈ Р̌ Ҏ Р̌ С̌ Ҫ С̣ С̱ Т́ Т̈ Т̌ Т̇ Т̣ Ҭ У̃ Ӳ У̊ Ӱ̄ Ұ Ү Ү́ Х̣ Х̱ Х̮ Х̑ Х̌ Ҳ Ӽ х̊ Ӿ ӿ̊ Һ Һ̈ Ԧ Ц̌ Ц̈ Ҵ Ҷ Ҷ̣ Ӵ Ӌ Ҹ Ч̇ Ч̣ Ҽ Ҿ Ш̣ ꚜ Ы̆ Ы̄ Ӹ ꚝ Ҍ Ҩ Э̆ Э̄ Э̇ Ӭ Ӭ́ Ӭ̄ Ю̆ Ю̈ Ю̄ Я̆ Я̄ Я̈ Ӏ ʼ ˮ
Archaic or unused letters
А̨ Б̀ Б̣ Б̱ В̀ Г̀ Г̧ Г̄ Г̓ Г̆ Ҕ̀ Ҕ̆ Ԁ Д̓ Д̀ Д̨ Ԃ Ꚁ Ꙣ Е̇ Е̨ Ж̀ Ж̑ Ꙃ Ꙅ Џ̆ Ꚅ Ꚅ̆ Ꙁ З̀ З̑ Ԅ Ԇ Ꚉ Ԫ Ꚃ Ꚕ І̂ І̣ І̨ Ј̵ Ј̃ Ꙉ К̓ К̀ К̆ Ӄ̆ К̑ К̇ К̈ К̄ Ԟ К̂ Л̀ Ԡ Ꙥ Ԉ Л̑ Л̇ Ԕ М̀ М̃ Ꙧ Н̀ Н̄ Н̧ Н̃ Ԋ Ԣ Н̡ Ѻ Ꙩ Ꙫ Ꙭ ꙮ Ꚙ Ꚛ П̓ П̀ П́ Ҧ П̧ П̑ Ҁ Ԛ̆ Р́ Р̀ Р̃ Ԗ С̀ С̈ Ԍ Ҫ̓ Т̓ Т̀ Ԏ Т̑ Ꚋ Т̧ Ꚍ Ꚍ̆ ОУ Ꙋ У̇ У̨ ꙋ́ Ф̑ Ф̓ Х́ Х̀ Х̆ Х̇ Х̧ Х̾ Х̓ һ̱ Ѡ Ꙍ Ѽ Ѿ Ꙡ Ц̀ Ц́ Ц̓ Ꚏ Ꚏ̆ Ꚑ Ч́ Ч̀ Ч̆ Ч̑ Ч̓ Ԭ Ꚓ Ꚇ Ꚇ̆ Ҽ̆ Ш̀ Ш̆ Ш̑ Щ̆ Ꚗ Ꚗ̆ Ъ̄ Ъ̈ Ъ̈̄ Ꙑ Ы̂ Ы̃ Ѣ́ Ѣ̈ Ѣ̆ Ꙓ Э̨ Э̂ Ꙕ Ю̂ Ꙗ Я̈ Я̂ Я̨ Ԙ Ѥ Ѧ Ꙙ Ѫ Ꙛ Ѩ Ꙝ Ѭ Ѯ Ѱ Ѳ Ѵ Ѷ Ꙟ
List of Cyrillic letters List of Cyrillic multigraphs
v t e

O (О о; italics: О о) is a letter of the Cyrillic script.

The letter most commonly represents the sound /ɔ/, like the o in "off". In Russian and Serbo-Croatian, it represents the sound /o/.

The Cyrillic letter О was derived from the Greek letter Omicron (Ο ο).

In modern-style typefaces, the Cyrillic letter O looks exactly like the Latin letter O ⟨O o⟩ and the Greek letter Omicron ⟨Ο ο⟩.

Historical typefaces (like poluustav (semi-uncial), a standard font style for the Church Slavonic typography) and old manuscripts represent several additional glyph variants of Cyrillic O, both for decorative and orthographic (sometimes also "hieroglyphic"^[1]) purposes, namely:

• broad variant (Ѻ/ѻ), used mostly as a word initial letter (see Broad On for more details);
• narrow variant, being used now in Synodal Church Slavonic editions as the first element of digraph Oy/oy (see Uk (Cyrillic) for more details), and in the editions of Old Believers for unstressed "o" as well;
• variant with a cross inside (Crossed O), Ꚛ, used in certain manuscripts as the initial letter of words окрестъ 'around, nearby' (the root of this Slavonic word, крест, means 'cross') and округъ 'district, neighbourhood' with their derivatives;
• "eyed" variant (Monocular O) with a dot inside (Ꙩ/ꙩ), used in certain manuscripts in spelling of word око 'eye' and its derivatives. In many other texts, including the birchbark letters, the monocular O was not used as a hieroglyph but largely as a synonym of Broad On signalling the word-initial position;
• "two-eyed" variants (Binocular O) with two dots inside (Ꙫ/ꙫ or Ꙭ/ꙭ), also double "O" without dots inside were used in certain manuscripts in spelling of dual/plural forms of the words with the same root 'eye';
• "many-eyed" variant (Multiocular O), ꙮ, used in certain manuscripts in spelling of the same root when embedded into word многоочитый 'many-eyed' (an attribute of seraphim).

In Russian, O is used word-initially, after another vowel, and after non-palatalized consonants. Because of a vowel reduction processes, the Russian /o/ phoneme may have a number of pronunciations in unstressed syllables, including [ɐ] and [ə].

In Macedonian, Bulgarian, Ukrainian and Belarusian, the letter represents the sound /ɔ/.

In Tuvan the Cyrillic letter can be written as a double vowel.^[2][3] It's the most common letter in the Russian language.^[4]

• Ο ο : Greek letter Omicron
• O o : Latin letter O
• 0 : Digit Zero
• Ё ё : Cyrillic letter Yo
• Ѻ ѻ : Cyrillic letter Broad On
• Ӧ ӧ : Cyrillic letter O with diaeresis
• Ө ө : Cyrillic letter Oe
• Ӫ ӫ : Cyrillic letter Oe with diaeresis
• Ҩ ҩ : Cyrillic letter O-hook

Exotic glyph variants of Cyrillic O are available only in Unicode:^{[5][6][7][8][9]}

• broad Ѻ/ѻ:
  • CYRILLIC CAPITAL LETTER ROUND OMEGA: U+047A
  • CYRILLIC SMALL LETTER ROUND OMEGA: U+047B
• narrow ᲂ does not just represent itself, but also used in digraph Oy/oy:
  • CYRILLIC SMALL LETTER NARROW O: U+1C82
  • CYRILLIC CAPITAL LETTER UK: U+0478 (deprecated in favor of combination of Cyrillic letters О and у, U+041E U+0443)
  • CYRILLIC SMALL LETTER UK: U+0479 (deprecated in favor of combination of Cyrillic letters о and у, U+043E U+0443 or U+1C82 U+0443)
• with a cross inside (Ꚛ/ꚛ):
  • CYRILLIC CAPITAL LETTER CROSSED O: U+A69A
  • CYRILLIC SMALL LETTER CROSSED O: U+A69B
• doubled Ꚙ/ꚙ:
  • CYRILLIC CAPITAL LETTER DOUBLE O: U+A698
  • CYRILLIC SMALL LETTER DOUBLE O: U+A699
• eyed Ꙩ/ꙩ:
  • CYRILLIC CAPITAL LETTER MONOCULAR O: U+A668
  • CYRILLIC SMALL LETTER MONOCULAR O: U+A669
• two-eyed (Ꙫ/ꙫ, Ꙭ/ꙭ):
  • CYRILLIC CAPITAL LETTER BINOCULAR O: U+A66A
  • CYRILLIC SMALL LETTER BINOCULAR O: U+A66B
  • CYRILLIC CAPITAL LETTER DOUBLE MONOCULAR O: U+A66C
  • CYRILLIC SMALL LETTER DOUBLE MONOCULAR O: U+A66D
• many-eyed ꙮ:
  • CYRILLIC LETTER MULTIOCULAR O: U+A66E
• combining O for Church Slavonic abbreviations (as трⷪца = троица '(Holy) Trinity'):
  • COMBINING CYRILLIC LETTER O: 2DEA

• The dictionary definition of О at Wiktionary
• The dictionary definition of о at Wiktionary