B is the second letter of the Latin alphabet. B may also refer to:

Science, technology, and mathematics

Astronomy

* Astronomical objects in the Barnard list of dark nebulae (abbreviation B) * Latitude (''b'') in the

galactic coordinate system The galactic coordinate system is a celestial coordinate system in spherical coordinates, with the Sun as its center, the primary direction aligned with the approximate center of the Milky Way Galaxy, and the fundamental plane parallel to an ap ...

Biology and medicine

Haplogroup B (mtDNA) In human mitochondrial genetics, haplogroup B is a human mitochondrial DNA (mtDNA) haplogroup. Origin Haplogroup B is believed to have arisen in Asia some 50,000 years before present. Its ancestral haplogroup was haplogroup R. The greatest vari ...

, a human mitochondrial DNA (mtDNA) haplogroup * Haplogroup B (Y-DNA), a Y-chromosomal DNA (Y-DNA) haplogroup * blood type, Blood type B * ATC code B ''Blood and blood forming organs'', a section of the Anatomical Therapeutic Chemical Classification System * Vitamin B * Hepatitis B * Berlin Botanical Garden and Botanical Museum, assigned the abbreviation B as a repository of herbarium specimens

Computing

* B (programming language) * B-Method, for computer software development * B-tree, a data structure * Bit (b) * Byte (B) * , an HTML element#b, HTML element denoting bold text

Physical and chemical quantities and units

* One of the reciprocal lattice vectors (''b*'') * Breadth (''b''); see length * Impact parameter (''b'') * Molality (''b'') * Barn (unit) (b), a unit of area * Magnetic field (''B'') * Napierian absorbance (''B'') * rigid rotor, Rotational constant (''B'') * Second virial coefficient (''B'') * Susceptance (''B'') * Bel (''B''), a logarithmic unit equal to ten decibels

Other uses in science, technology, and mathematics

* ''B'', a modal logic * Boolean domain (

\mathbb

), in mathematics * Boron, symbol B, a chemical element * Bulb (photography), a shutter-speed setting * B battery, a battery used to provide the plate voltage of a Battery (vacuum tube)#B battery, vacuum tube * B horizon, a layer of soil commonly known as subsoil * B, B+ and B−, expressions of buoyancy in convective available potential energy

Linguistics

* В, a letter of the Cyrillic alphabet * Voiced bilabial stop (b, in the International Phonetic Alphabet)

Arts and media

Music

Musical notation

* B (musical note) * B major, a scale * B minor, a scale * B major chord, Chord names and symbols (popular music) * Flat (music), a note lower in pitch by a semitone

Performers

* Beyoncé * B, member of Superorganism (band)

Recordings

* B (BamBam EP), ''B'' (BamBam EP), an extended play by BamBam * B (Battles EP), ''B'' (Battles EP), an extended play by Battles * B (I Am Kloot album), ''B'' (I Am Kloot album), a compilation album by I Am Kloot * b (Moxy Früvous EP), ''b'' (Moxy Früvous EP), an extended play by Moxy Früvous * "b", an Iamamiwhoami song * "B", a song by Todrick Hall from his 2018 album ''Forbidden (Todrick Hall album), Forbidden''

Other media

* /b/, a board on 4chan * the Baltimore Sun, ''b'' (newspaper), a free daily, tabloid sized newspaper, published by ''The Baltimore Sun'' * ''Codex Vaticanus Graecus 1209'', an ancient bible * Rajawali Televisi, previously named B Channel, a television channel in Indonesia * B, the production code for the 1963–64 ''Doctor Who'' serial ''The Daleks'' * B, a character in ''Total Drama: Revenge of the Island'' * ''"B" Is for Burglar'', the second novel in Sue Grafton's "Alphabet mystery" series, published in 1985

Places

* Belgium, on the vehicle registration plates of the European Union * Bucharest, on the Vehicle registration plates of Romania#County codes, vehicle registration plates of Romania

Sport

* Australian rules football positions#Full back, in Australian Rules football * B, often used after the name of football clubs to denote a reserve team

Transportation

* B (New York City Subway service) * B Line (Los Angeles Metro) * Line B (Buenos Aires Metro) * B (S-train), in Copenhagen * RER B, a line in the RER of Paris *Bundesstraße (federal highway) in Austria and Germany (abbreviation B) * Bayshore Route of Shuto Expressway in Japan, numbered as route B

Other uses

* B (grade), for evaluation of students' work * B (bank), a banking brand in the United Kingdom * Barnabites ( la, Clerici Regulares Sancti Pauli), a religious order abbreviated to the postnominal ''B.'' * List of military time zones#B, Bravo, the military time zone code for UTC+02:00 * Brutus, a Roman cognomen (abbreviation B) * Farmall B, a tractor produced by International Harvester from 1939 to 1947 * Dominical letter B for a common year starting on Saturday