U (У у; italics: У у or <span style="font-family: times, Times New Roman, serif; font-size: larger">У у</span>; italics: <span style="font-family: times, Times New Roman, serif; font-size: larger">У у</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>).
History
thumb|170px|U, from [[Alexandre Benois' 1904 alphabet book. It shows Ulitsa (street) and uraganʺ (hurricane).]]
thumb|170px|A [[PFM-1 training mine, distinguishable from the live version by the presence of the letter У (short for учебный, uchebnyy, "for training").]]
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 other languages
In Tuvan the Cyrillic letter can be written as a double vowel.
In certain languages, U is used to mark labialization.
Related letters and other similar characters
thumb|170px|Similarity with [[Y (uppercase): The grapheme on the left is clearly a Cyrillic U, the one in the middle may represent both letters, the one on the right is clearly a Greek or Latin Y.|class=skin-invert-image]]
- Υ υ : Greek letter Upsilon
- U u : Latin letter U
- Ú ú : Latin letter Ú
- Y y : Latin letter Y
- Ў ў : Cyrillic letter Short U, used in Belarusian, Dungan, Siberian Eskimo (Yuit), Uzbek
- Ӯ ӯ : Cyrillic letter U with macron, used in Tajik and Carpatho-Rusyn
- Ӱ ӱ : Cyrillic letter U with diaeresis, used in Altai (Oyrot), Khakas, Gagauz, Khanty, Mari
- Ӳ ӳ : Cyrillic letter U with double acute, used in Chuvash
- Ү ү : Cyrillic letter straight U, used in Mongolian, Kazakh, Tatar, Bashkir, Dungan and other languages
- Ұ ұ : Cyrillic letter Straight U with stroke, used in Kazakh
- Ꭹ Ꮍ : The syllables gi and mu of the Cherokee syllabary; Ꭹ (gi) notably appearing in the Cherokee self-designation ᏣᎳᎩ (Tsalagi)
- ע: The Hebrew letter Ayin
- У̊: Cyrillic letter U with ring, used in Shugnhi orthography.
