L4

L4 or L-4 may refer to :

Transportation

SP&S Class L-4, an 1884 steam locomotives class
USS L-4 (SS-43), a 1915 United States Navy L-class submarine
HMS L4, a 1918 British L class submarine
Lawson L-4, a 1924 American unflown biplane airliner
Piper Cub (U.S. military designation: L-4), an aircraft
Inline-four engine (L4), a type of inline internal combustion four cylinder engine
- Liberty L-4, a World War I four-cylinder, water-cooled, inline, aero-engine
Lynx Aviation (IATA code)
L4 (New York City bus), a temporary bus route in New York City
Parramatta Light Rail, also known as the L4, a light rail service in Parramatta, Sydney, Australia
Chaika L-4, a Russian twin-engined amphibious aircraft
Soviet submarine L-4

L4 microkernel family, a family of operating system kernels
L4, the transport layer in the OSI model of computer communications
L4, the fourth Lagrangian point in an astronomical orbital configuration
L⁴, an L^p space for p=4 (sometimes called Lebesgue spaces)
L-4, the fourth iteration of L-carrier, high capacity frequency division multiplex over coaxial cable used by the Bell System

Haplogroup L4 (mtDNA), a human mitochondrial DNA haplogroup
Ribosomal protein L4, a human gene
L4, a lumbar vertebra of the vertebral column, in human anatomy
The fourth and last larval stage in the Caenorhabditis elegans worm development