U (ã ÃÂ; italics: ã àor <span style="font-family: times, Times New Roman, serif; font-size: larger">ã ÃÂ</span>; italics: <span style="font-family: times, Times New Roman, serif; font-size: larger">ã ÃÂ</span>) is a letter of the Cyrillic script. It commonly represents the close back rounded vowel , somewhat like the pronunciation of in "boot" or "boo". The forms of the Cyrillic letter U are similar to the lowercase of the Latin letter Y (Y y; <span style="font-family: times, Times New Roman, serif; font-size: larger">Y y</span>).
Historically, Cyrillic U evolved as a specifically East Slavic short form of the digraph used in ancient Slavic texts to represent . The digraph was itself a direct loan from the Greek alphabet, where the combination (omicron-upsilon) was also used to represent . Later, the o was removed, leaving the modern upsilon-only form.
Consequently, the form of the letter is derived from Greek upsilon , which was parallelly also taken over into the Cyrillic alphabet in another form, as Izhitsa . (The letter Izhitsa was removed from the Russian alphabet in the orthography reform of 1917/19.)
It is normally romanised as "u", but in Kazakh, it is romanised as "w".
In the Cyrillic numeral system, the Cyrillic letter U had a value of 400.
In Tuvan the Cyrillic letter can be written as a double vowel.
In certain languages, U is used to mark labialization.