U with macron is used in the alphabet of the Tajik language, where it represents the close-mid central rounded vowel, /ɵ/. Accordingly, although the letter shape is a modification of ⟨У⟩, the only aspect of the sound shared with /u/ is that both are relatively close, rounded vowels.
In 1937, it was also proposed for use in the Karelian Cyrillic alphabet to represent /y/, but was not adopted.
U with macron is used to represent long /u/ in Kildin Sami and Mansi, two Uralic languages spoken on the Kola peninsula (Kildin) and Western Siberia (Mansi). In these languages, length is distinctive, and the macron is used to mark the long version of all the vowels.
U with macron is also used in the Aleut language (Bering dialect).[2] It is the thirty-sixth letter of the modern Aleut alphabet.
U with macron is also used in Carpatho-Rusyn, the only Slavic language to do so. Its sound is close to /y/, or in some dialects, /u/.[3][4]
^Головко, Е. В. (1994). Словарь алеутско-русский и русско-алеутский (беринговский диалект) [Aleut-Russian and Russian-Aleut Dictionary (Bering dialect)]. Отд-ние изд-ва "Просвещение". p. 14. ISBN5-09-002312-3.