U (disambiguation)

U, or u, is the twenty-first letter of the English alphabet.

U may also refer to:

Mathematics

 * $$\cup$$, union (set theory)
 * U-set, a set of uniqueness
 * U, the unitary group

Chemistry

 * Uranium, symbol U, a chemical element
 * u, the Dalton (unit), a unified atomic mass unit to express atomic and molecular masses

Astronomy

 * U, ultraviolet magnitude, in a UBV photometric system
 * U, an October 16 through 31 discovery in the provisional designation of a comet
 * U (trans-Neptunian object), a possible extremely distant trans-Neptunian object

Computing

 * , a now-deprecated HTML element denoting underlined text
 * U, representing 1.75" as the minimal height of a rack unit
 * U, representing a 10x10x10cm CubeSat
 * U, universal Turing machine

Biology

 * U, abbreviation for uracil
 * U, mitochondrial haplogroup U

Other scientific uses

 * U, a common notation for potential energy
 * U, the middle of an edge joining a hexagonal and a square face of the Brillouin zone of a face-centered cubic lattice, in solid-state physics
 * U, one of the two subcarrier-modulated color-difference channels in the YUV colorspace, in video
 * U, the recommended symbol for a system's internal energy, in thermodynamics
 * U, units, any of various standard units of biological activity, such as insulin units, enzyme units, or penicillin units
 * U, the enzyme unit
 * International units, for which the symbol U is sometimes used
 * U, the abbreviation for selenocysteine, an uncommon amino acid containing selenium
 * u, the alternative abbreviation for the SI prefix "micro-" when the Greek letter mu (μ) is not available
 * U or U-value, the symbol for the overall heat transfer coefficient or thermal transmittance

Transportation

 * U Line, also known as the Uijeongbu Line, a light metro line in Seoul
 * Transilien Line U, a line of the Paris transport network
 * U (Los Angeles Railway), a former streetcar line in Los Angeles
 * Yurikamome, an automated guideway line in Tokyo, labeled Yurikamome line symbol.svg
 * The official West Japan Railway Company service symbol for:
 * JRW kinki-U.svg Sakurai Line.
 * JRW oka-U.svg Kibi Line.

Music

 * ’u’, the first opera in the Klingon language
 * "U" (Kendrick Lamar song), 2015
 * "U" (Super Junior song), 2006
 * U (Incredible String Band album), 1970
 * U (NiziU album), 2021
 * U (Tourist album), 2016 album by Tourist
 * "U", a song by KNK from Remain
 * "U", a song by Pearl Jam on their album Lost Dogs
 * "U", a song by S.E.S., released in 2002
 * "U", an album by The Enid, released in 2019
 * "U", a song by Treasure (band), released in 2022

People

 * An honorific used in Burmese names
 * An alternative spelling of Woo (Korean surname), including a list of people with that family name
 * An alternative spelling of Woo (Korean given name), including a list of people with that given name
 * U of Goryeo (1363–1389), king of Goryeo (Korea), often called King Woo

Places

 * U, Federated States of Micronesia
 * Ü-Tsang, one of three historical provinces of Tibet
 * Ü (region), a particular region of Ü-Tsang

Language

 * /u/, the close back rounded vowel in the International Phonetic Alphabet
 * U language, a language spoken by about 40,000 people in the Yunnan Province of China
 * U (cuneiform), a cuneiform sign
 * U (Cyrillic), a letter of the Cyrillic script
 * U (kana), a Japanese syllabary symbol
 * U and non-U English, sociolectal varieties of British English
 * Ս, glyph for the Armenian letter se
 * u, an abbreviation for "you" in computer chats
 * U-, a prefix used for German submarines during World War II
 * U, a title roughly equal to "Mister" in Burmese
 * The Greek letter μ

Film and television

 * U (film), a 2006 French animated feature film directed by Serge Elissalde and Grégoire Solotareff
 * The U (film), a 2009 documentary about the Miami Hurricanes football team
 * U (Universal), a media content rating used in the following countries:
 * United Kingdom, issued by the British Board of Film Classification
 * India, issued by the Central Board of Film Certification
 * Malaysia, issued by the Film Censorship Board of Malaysia
 * France, documented at Censorship in France
 * India, Latvia, Malta, Mauritius and Slovakia, documented at Motion picture content rating system and Television content rating system
 * U (TV channel), a former television channel in New Zealand
 * U, the production code for the 1965 Doctor Who serial The Myth Makers
 * The American Spanish-language network Univisión has the U logo
 * U (streaming service), (formerly UKTV Play) a free British streaming service owned by UKTV

Other uses

 * University, commonly abbreviated "U"
 * U Mobile, Malaysian mobile phone and data service provider
 * U-bend, a U-shaped plumbing trap
 * U-bolt, a U-shaped metal fastener
 * Ⓤ, (U inside a circle), hechsher or kosher certification by the Orthodox Union
 * U, =U= or -U-, symbol for Ustaše Croatian movement
 * Nickname for football teams:
 * La U or Universitario de Deportes, Peru
 * Universitatea Cluj, Romania
 * U, the color blue in Magic: The Gathering
 * Wii U, the sixth Nintendo video game home console, released in 2012
 * Uniform, the military time zone code for UTC−08:00
 * "U" Is for Undertow, the twenty-first novel in Sue Grafton's "Alphabet" mystery series, published in 2009
 * Underscore, originally invoked in HTML using
 * U, a brand of menstrual hygiene products by Kotex
 * U, the logo for Unilever