E2

E2, e2, E02, E.II, e$2$ or E-2 may refer to:

Science and technology

 * E2 reaction, a type of elimination reaction
 * Honda E2, one of the predecessors of Honda's ASIMO robot
 * E2, a communications channel defined in the E-carrier standard
 * G2 (mathematics) (old name E2 or E2), a group

Biology and medicine

 * Ubiquitin-conjugating enzyme, a protein component of proteasome-mediated protein degradation
 * E2 regulatory sequence, for the insulin gene
 * Levuglandin E2, an aldehyde
 * Prostaglandin E2, an abortifacient
 * Prostaglandin E2 receptor, a human gene
 * Iodine-deficiency (ICD-10 code: E02)
 * Estradiol, an estrogen steroid hormone
 * Dihydrolipoyl transacetylase, the second element of the multienzyme pyruvate dehydrogenase complex
 * Acireductone dioxygenase (iron(II)-requiring), an enzyme
 * Haplogroup E2 (Y-DNA), a human Y-chromosome DNA haplogroup

Computing

 * E2 (cipher), a block cipher submitted to the AES competition by NTT
 * Tungsten E2, a business-class Palm OS-based handheld computer
 * Motorola ROKR E2, a smartphone
 * Everything2, a collaborative web-based community consisting of a database of interlinked user-submitted written material

Arts and entertainment

 * E$2$ (album), a 2007 album by Eros Ramazzotti

Television

 * "E²", an episode of Star Trek: Enterprise
 * MTV e2, a Canadian entertainment news program that airs on MTV Canada
 * E2 (TV channel), a Turkish TV channel
 * e2 by SKY PerfecTV!, a satellite television service in Japan operated by SKY Perfect

Air

 * Northrop Grumman E-2 Hawkeye, an American carrier-based AWACS aircraft
 * Fokker E.II, a 1915 German single-seat monoplane fighter aircraft
 * Pfalz E.II, a German aircraft powered by the Oberursel U.I engine
 * Taylor E-2, a small, light and simple utility aircraft
 * Embraer E-Jet E2 family, an updated version of the E-jet family
 * Eastman E-2 Sea Rover, a 1920s seaplane
 * Eurowings Europe (former IATA code: E2), an Austrian airline subsidiary of Lufthansa
 * Kampuchea Airlines (former IATA code: E2), a Cambodian airline

Rail

 * E2 Series Shinkansen, a Japanese high-speed train
 * EMC E2, an early American passenger-train diesel locomotive
 * LB&SCR E2 class, a class of 0-6-0T steam locomotives designed by Lawson Billington
 * PRR E2, an American PRR 4-4-2 locomotive
 * CNW Class E-2, a class of 4-6-2 steam locomotives built by the American Locomotive Company in 1923

Roads and footpaths

 * E02 expressway (Sri Lanka), in Sri Lanka
 * E2 European long distance path, a long-distance footpath that runs from Galway in Ireland to France's Mediterranean coast
 * North–South Expressway Southern Route (E2), in Malaysia
 * European route E002, in Azerbaijan and Armenia
 * E2 expressway (Philippines), expressway route in the Philippines
 * San'yō Expressway (route E2), Hiroshiwa-Iwakuni Road, Ogori Road and Yamaguchi-Ube Road, in Japan

Submarines

 * HMS E2, an E-class submarine of the Royal Navy
 * USS E-2, an E-class submarine of the US Navy

Other transport

 * London Buses route E2, England

Other uses

 * E-2 visa, a type of US visa
 * E2, a postcode district in the E postcode area for east London, England
 * Private E-2, a pay grade for the rank of Private in the US Army
 * E2 (nightclub), a nightclub in Chicago, US
 * Eternity II puzzle, a puzzle competition
 * E-II Holdings, Inc., an investment holding company formerly owned by Meshulam Riklis, and later by Carl Icahn
 * E2 grade, an assessment of difficulty in rock climbing