O with diaeresis (Cyrillic)

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

In Komi, it represents the schwa /ə/, like the ⟨a⟩ in "allow".

In Kurdish, it represents the near-close near-back rounded vowel /ʊ/, like the ⟨oo⟩ in "book".

In Mari, it represents the open-mid front rounded vowel /œ/, like the ⟨o⟩ in "boat".

In Udmurt, it represents the open-mid back unrounded vowel /ʌ/, like the ⟨u⟩ in "up".

In Russian books until the beginning of the 20th century, the letter Ӧ has been sporadically used instead of Ё in foreign names and loanwords (for example, the city of Cologne, Germany, which is Köln in German, might have been rendered in Russian as "Кӧльн").^[1]

In Tatar, this letter appeared in the 1861 Cyrillic orthography by Nikolay Ilminsky. This letter was replaced by Ө in 1939.

O with diaeresis and macron (Ӧ̄ ӧ̄; italics: Ӧ̄ ӧ̄) is a letter from the Cyrillic script. It is used in the southern dialects of the Selkup language, to indicate a long Ӧ.

• Ö ö : Latin letter O with diaeresis - an Azerbaijani, Estonian, Finnish, German, Hungarian, Icelandic, Swedish, Turkish, and Turkmen letter.
• Ơ ơ : Latin letter O with horn, used in Vietnamese language
• Ø ø : Latin letter O with stroke
• Õ õ : Latin letter O with tilde, used in Estonian
• Œ œ : Ligature Oe
• О о : Cyrillic letter O
• Ө ө : Cyrillic letter Oe
• Ӫ ӫ : Cyrillic letter Oe with diaeresis
• Cyrillic characters in Unicode