O with an ogonek (majuscule: Ǫ, minuscule: ǫ) is a letter of the Latin alphabet formed by the addition of the ogonek (from Polish: little tail) to the letter O. It is used in Western Apache, Mescalero-Chiricahua, Muscogee, Dadibi, Gwichʼin, Erie, and Navajo. In such languages, it represents either a nasalized close-mid back rounded vowel ([õ]), or a nasalized ([ɔ̃]).
It is also used in the Latin transcription of Old Church Slavonic where it represents the nasal back vowel, as well as in the Proto-Slavic language where it represents a labialized non-front vowel. It is also used in the Slavistic Phonetic Alphabet, where it represents the nasalized O-sound, for example, the pronunciation of Ą in Polish.
It was used in Old Norse, where it represented the open back rounded vowel ([ɒ]) sound. Additionally, the letter sporadically used to be an alternative to Ą in Polish.
In academic transcription of Vulgar Latin, Ǫ represents the open-mid vowel (contrasted with the close-mid vowel , represented with an underdot (Ọ)).