J (disambiguation)

J, or j, is the tenth letter of the English alphabet.

J may also refer to:

• Palatal approximant in the International Phonetic Alphabet
• J, Cyrillic letter Je

Astronomy

• J, a provisional designation prefix for some objects discovered between May 1 and 15 of a year

Computing

• J (programming language), successor to APL
• J# programming language for the Microsoft .NET Framework
• J operator, a programming construct
• J (operating system), an operating system for ICL's System 4 series of computers

Genetics and medicine

• Haplogroup J (mtDNA)
• Haplogroup J (Y-DNA)
• ATC code J Antiinfectives for systemic use, a section of the Anatomical Therapeutic Chemical Classification System

Mathematics

• J, symbol used to denote the Bessel function
• j, used as the symbol for the imaginary unit (${\sqrt {-1}}$) in fields where i is used for a different purpose (such as electric current)
• j and j² (or ${\bar {j}}$) are also used for the complex cube roots of unity
• j, a number with the property j ² = +1, used in the definition of the split-complex numbers
• j, the second imaginary unit of a quaternion
• j, an index variable in a matrix
• The j-invariant, a modular function

Physics and chemistry

• J, Joule, the SI unit of energy
• J, the SI-recommended dimension symbol for luminous intensity, conventionally rendered in a sans-serif typeface
• j →, current density
• second moment of area
• J, name given by Samuel C. C. Ting for the J/ψ particle
• J-coupling, indirect dipole-dipole coupling between two nuclear spins
• J (element), atomic symbol of Jod, German for iodine

Music

• J, stage name of Jang Ye-eun, a member of the K-Pop group STAYC
• J (Korean singer), a Korean pop singer
• J (musician), a Japanese rock musician
• J., nickname of American White Zombie guitarist Jay Yuenger
• J., stage name of German musician Jaye Muller
• J Mascis, American singer and guitarist of Dinosaur Jr.
• J Records, a record label

Albums

• J (Jaehyun album), album by South Korean singer Jaehyun

Songs

• "J", song by Reggie and the Full Effect from the album Last Stop: Crappy Town
• "J", song by Mindless Self Indulgence from the album Frankenstein Girls Will Seem Strangely Sexy

Film and television

• Agent J, a character in the Men in Black films portrayed by Will Smith
• J, an antagonist in Bobobo
• Kamen Rider J, a Japanese movie
• J, the production code for the 1964 Doctor Who serial Planet of Giants
• Serial Designation "J", one of the antagonists from the webseries Murder Drones (2021-2024)

Writers

• J (sometimes given as I), pen name of the Danish novelist Cornelia von Levetzow (1836–1921)

Transportation

• J (Los Angeles Railway)
• J (New York City Subway service)
• J Church (San Francisco Muni)
• J Line (Los Angeles Metro)
• NZR J Class, a 4-8-2 type class of steam locomotive used by New Zealand Railways
• Transilien Line J, a line of the Paris transport network
• , the official West Japan Railway Company service symbol for the Bantan Line
• Saviem J, also known as the Renault J, a range of medium-duty trucks

Other uses

• J, slang for joint (cannabis)
• J, slang for Air Jordan shoes
• J, slang for a jump shot in basketball
• J band (disambiguation)
• J (psychedelic), an entactogenic drug
• Elgin, Joliet and Eastern Railway, a Chicago railway sometimes referred to as "The J"
• J, the international license plate code for Japan
• J, the Canadian postal code for the western and northern regions of Quebec
• J, German mint mark for the city of Hamburg
• J abbreviation for Jahwist, one of the hypothesized major authors of the Torah
• J, an abbreviated title of a High Court judge (in Law Reports, etc.), e.g. Bloggs J
• J. The Jewish News of Northern California, a weekly newspaper serving the Jewish community in Northern California
• J, the narrator of Jerome K. Jerome's novel Three Men in a Boat
• J., Jezper Söderlund, the trance artist
• Lamborghini Aventador J, a 2012 Lamborghini supercar
• J (novel), a 2014 novel by Howard Jacobson
• ʲ, the symbol for Palatalization in the IPA
• Juliet, sometimes used as the unofficial military time zone code for local time
• "J" Is for Judgment, the tenth novel in Sue Grafton's "Alphabet mystery" series, published in 1993
• Guy Big J, range of trucks produced by Guy Motors of England between 1964 and 1978
• [J], code for academic journal in the reference section of an academic work

See also

• J/22, J/24 and J/80 sailboat classes
• J Mays, Group Vice President of Design and Chief Creative Officer at Ford Motor Company
• J Dilla, a hip-hip performer and producer
• Jay-Z, a hip-hop performer
• Jay (disambiguation)
• Jay Jay, a 2003 film
• JJJ (disambiguation)