U (У у; italics: У у) is a letter of the Cyrillic script. It commonly represents the close back rounded vowel/u/, somewhat like the pronunciation of ⟨oo⟩ in "boot". The forms of the Cyrillic letter U are similar to the lowercase of the Latin letter Y (Y y; Y y), but, as with most Cyrillic letters, the upper and lowercase forms are similar in shape differing mainly in size and vertical placement.
Historically, Cyrillic U evolved as a specifically East Slavic short form of the digraph ⟨оу⟩ used in ancient Slavic texts to represent /u/. The digraph was itself a direct loan from the Greek alphabet, where the combination ⟨ου⟩ (omicron-upsilon) was also used to represent /u/.
^However, many Dungan books are in fact set using Ӯ (with macron) instead of Ў with breve, e.g. the Dungan-Russian dictionary (1968). There is never an ambiguity, as this is the only У-with-a-diacritic in Dungan. It is used in Dungan syllables where pinyin would use -u, except in those with labial consonants (i.e. in du, ' nu, lu, gu, hu, zu, ru, etc., but not bu or mu)