J, or j, is the tenth letter of the English alphabet. J may also refer to: *

Palatal approximant The voiced palatal approximant is a type of consonant used in many spoken languages. The symbol in the International Phonetic Alphabet that represents this sound is ; the equivalent X-SAMPA symbol is j, and in the Americanist phonetic notation i ...

in the International Phonetic Alphabet * J, Cyrillic letter Je

Astronomy

* J, a

provisional designation Provisional designation in astronomy is the naming convention applied to astronomical objects immediately following their discovery. The provisional designation is usually superseded by a permanent designation once a reliable orbit has been calcu ...

prefix for some objects discovered between May 1 and 15 of a year

Computing

J (programming language) The J programming language, developed in the early 1990s by Kenneth E. Iverson and Roger Hui, is an array programming language based primarily on APL (also by Iverson). To avoid repeating the APL special-character problem, J uses only the ba ...

, successor to APL * J# programming language for the Microsoft .NET Framework *

J operator In computer science, Peter Landin's J operator is a programming construct that post-composes a lambda expression with the continuation to the current lambda-context. The resulting “function” is first-class and can be passed on to subsequent ...

, 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 is a human mitochondrial DNA (mtDNA) haplogroup. The clade derives from the haplogroup JT, which also gave rise to haplogroup T. Within the field of medical genetics, certain polymorphisms specific to haplogroup J have been asso ...

Haplogroup J (Y-DNA) Haplogroup J-M304, also known as J,ISOGG] ''Y-DNA Haplogroup J and its Subclades - 2016'' (2 February 2016). is a human Y-chromosome DNA haplogroup. It is believed to have evolved in the Caucasus or Iran.' The clade spread from there during t ...

* 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 Bessel functions, named after Friedrich Bessel who was the first to systematically study them in 1824, are canonical solutions of Bessel's differential equation x^2 \frac + x \frac + \left(x^2 - \alpha^2 \right)y = 0 for an arbitrary complex ...

* ''j'', used as the symbol for the

imaginary unit The imaginary unit or unit imaginary number () is a mathematical constant that is a solution to the quadratic equation Although there is no real number with this property, can be used to extend the real numbers to what are called complex num ...

(

\sqrt

) in fields where ''i'' is used for a different purpose (such as electric current) * ''j'' and ''j²'' (or

\bar

) are also used for the complex cube

roots of unity In mathematics, a root of unity is any complex number that yields 1 when raised to some positive integer power . Roots of unity are used in many branches of mathematics, and are especially important in number theory, the theory of group char ...

* ''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 In mathematics, the quaternion number system extends the complex numbers. Quaternions were first described by the Irish mathematician William Rowan Hamilton in 1843 and applied to mechanics in three-dimensional space. The algebra of quater ...

* , an index variable in a

matrix Matrix (: matrices or matrixes) or MATRIX may refer to: Science and mathematics * Matrix (mathematics), a rectangular array of numbers, symbols or expressions * Matrix (logic), part of a formula in prenex normal form * Matrix (biology), the m ...

* The

j-invariant In mathematics, Felix Klein's -invariant or function is a modular function of weight zero for the special linear group \operatorname(2,\Z) defined on the upper half-plane of complex numbers. It is the unique such function that is holomorphic a ...

, a modular function

Physics and chemistry

* J,

Joule The joule ( , or ; symbol: J) is the unit of energy in the International System of Units (SI). In terms of SI base units, one joule corresponds to one kilogram- metre squared per second squared One joule is equal to the amount of work d ...

, the SI unit of energy * J, the SI-recommended dimension symbol for

luminous intensity In photometry, luminous intensity is a measure of the wavelength-weighted power emitted by a light source in a particular direction per unit solid angle, based on the luminosity function, a standardized model of the sensitivity of the huma ...

, conventionally rendered in a sans-serif typeface * ,

current density In electromagnetism, current density is the amount of charge per unit time that flows through a unit area of a chosen cross section. The current density vector is defined as a vector whose magnitude is the electric current per cross-sectional ...

second moment of area The second moment of area, or second area moment, or quadratic moment of area and also known as the area moment of inertia, is a geometrical property of an area which reflects how its points are distributed with regard to an arbitrary axis. Th ...

* J, name given by Samuel C. C. Ting for the

J/ψ particle The (J/psi) meson is a subatomic particle, a flavor-neutral meson consisting of a charm quark and a charm antiquark. Mesons formed by a bound state of a charm quark and a charm anti-quark are generally known as " charmonium" or psions. Th ...

J-coupling In nuclear chemistry and nuclear physics, ''J''-couplings (also called spin-spin coupling or indirect dipole–dipole coupling) are mediated through chemical bonds connecting two spins. It is an indirect interaction between two nuclear spins tha ...

, indirect dipole-dipole coupling between two nuclear spins *

J (element) Iodine is a chemical element; it has Chemical symbol, symbol I and atomic number 53. The heaviest of the stable halogens, it exists at Standard temperature and pressure, standard conditions as a semi-lustrous, non-metallic solid that melts t ...

, 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), ''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 web series ''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, J Church (San Francisco Muni) * J Line (Los Angeles Metro) * NZR J class (1939), 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 * JRW kinki-J

, 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 * "The J", a nickname for the Elgin, Joliet and Eastern Railway, a former railroad

Other uses

* J, slang for joint (cannabis) * J, slang for Air Jordan shoes * J, slang for a glossary of basketball terms#J, 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 Identifying marks on euro coins#Mint marks, 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 (England and Wales), 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), ''J'' (novel), a 2014 novel by Howard Jacobson * ''ʲ'', the symbol for Palatalization_(phonetics), Palatalization in the IPA * Juliet, sometimes used as the unofficial List of military time zones, 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