O with diaeresis (Cyrillic)

Slavic letters
А Б В Г Ґ Д Ђ Ѓ Е Ѐ Ё Є Ж З Ѕ И Ѝ І Ї Й Ј К Л Љ М Н Њ О П Р С Т Ћ Ќ У Ў Ф Х Ц Ч Џ Ш Щ Ъ Ы Ь Э Ю Я
Non-Slavic letters
Ӑ А̄ А̊ А̃ Ӓ Ӓ̄ Ә Ә́ Ә̃ Ӛ Ӕ Ғ Г̧ Г̑ Г̄ Ҕ Ӻ Ӷ Ԁ Ԃ Ꚃ Ꚁ Ꚉ Ԫ Ԭ С́ Ӗ Е̄ Е̃ Ё̄ Є̈ Ӂ Җ Ꚅ Ӝ Ԅ Ҙ Ӟ З́ Ԑ Ԑ̈ Ӡ Ԇ Ӣ И̃ Ҋ Ӥ Қ Ӄ Ҡ Ҟ Ҝ Ԟ Ԛ Ӆ Ԯ Ԓ Ԡ Ԉ Ԕ Ӎ Ӊ Ң Ԩ Ӈ Ҥ Ԣ Ԋ О̆ О̃ О̄ Ӧ Ө Ө̄ Ӫ Ҩ Ԥ Ҧ Р̌ Ҏ Ԗ Ҫ Ԍ Ꚑ Ҭ Ꚋ Ꚍ Ԏ У̃ Ӯ Ӱ Ӱ́ Ӳ Ү Ү́ Ұ Х̑ Ҳ Ӽ Ӿ Һ Һ̈ Ԧ Ꚕ Ҵ Ꚏ Ҷ Ӵ Ӌ Ҹ Ꚓ Ꚗ Ꚇ Ҽ Ҿ Ы̆ Ы̄ Ӹ Ҍ Э̆ Э̄ Э̇ Ӭ Ӭ́ Ӭ̄ Ю̆ Ю̈ Ю̈́ Ю̄ Я̆ Я̄ Я̈ Ԙ Ԝ Ӏ
Archaic letters
Ꙁ Ꙃ Ꙅ Ꙇ Ꙉ Ҁ Ѻ ОУ Ꙋ Ѡ Ѽ Ꙍ Ѿ Ꙏ Ѣ Ꙑ Ꙓ Ꙕ Ꙗ Ѥ Ѧ Ꙙ Ѫ Ꙛ Ѩ Ꙝ Ѭ Ѯ Ѱ Ѳ Ѵ Ѷ Ꙟ Ꙡ Ꙣ Ꙥ Ꙧ Ꙩ Ꙫ Ꙭ ꙮ Ꚙ Ꚛ
List of Cyrillic letters Cyrillic digraphs

O with diaeresis (Ӧ ӧ; italics: Ӧ ӧ) is a letter of the Cyrillic script. In all its forms it looks exactly like the Latin letter Ö (Ö ö Ö ö).

O with diaeresis is used in the alphabets of the Altay, Khakas, Komi, Kurdish, Mari, Shor and Udmurt languages.

In Altay, Khakas and Shor, it represents the close-mid front rounded vowel /ø/.

In Komi, it represents the schwa /ə/.

In Kurdish, it represents the close back rounded vowel /u/.

In Mari, it represents the open-mid front rounded vowel /œ/.

In Udmurt, it represents the open-mid back unrounded vowel /ʌ/.

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Wikipedia