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 Chaika L-4, a Russian twin-engined amphibious aircraft Soviet submarine L-4 Science and technology 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 Lp 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 Biology 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 Other uses L4, a modern version of the Bren light machine gun in the British Army ISO/IEC 8859-4 (Latin-4), an 8-bit character encoding See also L04 (disambiguation) Level 4 (disambiguation) 4L (disambiguation)