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 () in fields where i is used for a different purpose (such as electric current)
- j and j (or ) are also used for the complex cube roots of unity
- j, a number with the property j = +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
- , 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)
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