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L1, L01, L.1, L 1 or L-1 may refer to:

Mathematics, science and technology

Math

*L₁ distance in mathematics, used in taxicab geometry
* L¹, the space of Lebesgue integrable functions
* ℓ¹, the space of absolutely convergent sequences

Science

* L1 family, a protein family of cell adhesion molecules
*L1 (protein), a cell adhesion molecule
*, Lagrangian point 1, the most intuitive position for an object to be gravitationally stationary relative to two larger objects (such as a satellite with respect to the Earth and Moon)
*Anthranilic acid, also called vitamin L1
*The first lumbar vertebra of the vertebral column in human anatomy
* The first larval stage in the '' Caenorhabditis elegans'' worm development

Technology

*L1, one of the frequencies used by GPS systems (see GPS frequencies)
*L1, the common name for the Soviet space effort known formally as Soyuz 7K-L1, designed to launch men from the Earth to circle the Moon without going into lunar orbit
* ISO/IEC 8859-1 (Latin-1), an 8-bit character encoding
* An L-carrier cable system developed by AT&T
* The level-1 CPU cache in a computer
* Sony Xperia L1, an Android smartphone
*A class of FM broadcast station in North America

Transportation and military

* Lehrgeschwader 1, from its historic ''Geschwaderkennung'' code with the Luftwaffe in World War II
* Lufthansa Systems' IATA code
* Lawrance L-1, a predecessor of the 1920s American Lawrance J-1 aircraft engine
* Inner West Light Rail, a light rail service in Sydney, Australia, numbered L1
* L1 (New York City bus), a temporary bus route in New York City
* Volkswagen L1, a Volkswagen concept hybrid car
* L1A1 Self-Loading Rifle

Locomotives

* Erie L-1, an American 0-8-8-0 steam locomotive class
* GCR Class 1B, latterly known as LNER Class L1, a class of British 2-6-4T steam locomotives
* GNR Class L1, latterly known as LNER Class R1, a class of British 0-8-2T steam locomotives
* LNER Thompson Class L1, a class of British 2-6-4T steam locomotives
* NCC Class L1, a Northern Counties Committee 0-6-0 class steam locomotive
* Pennsylvania Railroad class L1s, an American 2-8-2 steam locomotive class
* Soo Line L-1 class, an American 2-8-2 steam locomotive class
* SP&S Class L-1, an American 4-4-0 steam locomotive class
* SR L1 class, a class of 4-4-0 steam locomotives of Great Britain
* VR Class Vr1 (originally L1), a Finnish steam locomotive class

Aircraft

* Arado L 1, a 1929 German two-seat parasol-wing sporting monoplane
* Macchi L.1, a 1915 Austro-Hungarian reconnaissance flying boat
* Stinson L-1 Vigilant, the US Army Air Forces designation for the Stinson Model 74 observation aircraft

Submarines

* USS L-1 (SS-40), a 1915 United States Navy L-class submarine
* HMS L1, a Royal Navy submarine

Other

* Ligue 1, the top division of French football
* LINE1 or L1, a transposable element in DNA
* Lowest unique bid

*L1, in linguistics, a subject's first language or mother tongue
* L-1 Identity Solutions, a US face-recognition corporation
*L-1 visa, a document used to enter the United States for the purpose of work
* L1, an abbreviation denoting someone is a Level 1 Judge, in reference to Magic: The Gathering
* Bose L1 Portable Systems
* L=1, a lunar eclipse classification on the Danjon scale
* L1, the postcode for central Liverpool, a major UK city

;Containing L1

* ATC code L01 ''Antineoplastic agents'', a subgroup of the Anatomical Therapeutic Chemical Classification System
*Barcelona Metro line 1
* DSC-L1, a 2004 Sony Cyber-shot L series camera model
*Haplogroup L1 (mtDNA), a human mitochondrial haplogroup from Africa
*Luxo L-1, a lamp
* Panasonic Lumix DMC-L1, a 2006 single-lens reflex camera

See also

* Level 1 (disambiguation)

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