# L2

L2, L$^2$, L02, L II, L.2 or L-2 may refer to:

## Astronomy

* L$_2$ point, second Lagrangian point in a two body orbiting system
* L$_2$ Puppis, star which is also known as HD 56096
* Advanced Telescope for High Energy Astrophysics, a proposed X-ray telescope

## Biology

* Haplogroup L2 (mtDNA) in human genetics
* ATC code L02 Endocrine therapy, a subgroup of the Anatomical Therapeutic Chemical Classification System
* the second lumbar vertebrae of the vertebral column in human anatomy
* the second larval stage in the Caenorhabditis elegans worm development

## Computing

* L2 cache, the Level-2 CPU cache in a computer
* Layer 2 of the OSI model, in computer networking
* L2 (operating system), or Liedtke 2 (a.k.a. EUMEL/ELAN), a persistent microkernel operating system developed by German computer scientist Jochen Liedtke
* L2 (programming language)
* ISO/IEC 8859-2 (Latin-2), an 8-bit character encoding

## Entertainment

* L2 (music group), an American pop duo
* L2: Empuraan, a 2024 Indian film
* Leprechaun 2, a 1994 American film
* Lineage II, a 2003 MMO game
* Lumines II, a 2006 puzzle game

## Mathematics

* The L$^2$ space of square-integrable functions
* L$^2$ norm
* The ℓ$^2$ space of square-summable sequences
* L$^2$ cohomology, a cohomology theory for smooth non-compact manifolds with Riemannian metric
* L$_2$(n), the family of 2-dimensional projective special linear groups on finite fields.
* Ridge regression, regression and regularization method also known as L2 regularization

## Technology and weapons

* a variety of low-alloy special purpose steel
* a L-carrier cable system developed by AT&T
* a series of fragmentation hand grenades used by the British armed forces (American M61 copies), before being replaced by the L109 grenade
* the L designation given to the Sterling submachine gun in the British armed forces
* a frequency used in GPS satellite navigation signals, see GPS signals, a newer version is the L2C frequency

## Transportation
### Aircraft

* LZ 18 (L 2), a short-lived 1913 German airship (Imperial Navy designation: L 2)
* Arado L II, a 1929 German model of high-wing sporting monoplane
* ASJA L2, a pair of 1932 Swedish trainer biplanes
* Lawson L-2, a 1920 American biplane airliner
* Macchi L.2, an Italian model of biplane flying boat
* L-2 Grasshopper, an American Taylorcraft model used in WWII
* PZL Ł.2, a 1929 Polish model of liaison aircraft

### Aviation

* Junkers L2, an engine model; precursor to the Junkers L5
* Lynden Air Cargo, Alaskan airline (IATA code: L2)
* Walker County Airport (or Bevill Field), Alabama, U.S. (former FAA LID: L02)

### Rail locomotives

* Chesapeake and Ohio Class L-2 and L-2a, an American 4-6-4 "Hudson" type steam locomotives model
* Milwaukee Road class L2, an American 2-8-2 "Mikado" type steam locomotive
* SP&S Class L-2, an 1881 steam locomotives class
* LNER Class L2, a 1925 class of 2-6-4Ts

### Other modes of transport

* L2 (New York City bus), a temporary bus route in New York City, U.S.
* The Randwick branch of the CBD and South East Light Rail in Sydney, Australia, numbered L2

## Other uses

* Second language (L2), a non-native, acquired tongue of an individual
* L², a Flemish political youth organization
* L-2 visa, a U.S. travel document for dependents of temporary workers
* a class of FM radio broadcasting in North America
* Ligue 2, a French association football league
* L2 Inc, an American market research company