in science and technology C4, butyl-type hydrocarbon chain, a type of four-carbon molecule, especially in C4 reversed-phase chromatography columns Cluster 4 or Tango, an ESA satellite that studies the Earth's magnetosphere over the course of an entire solar cycle Organizations C4 (Colombia), a political party in Colombia C4, a social welfare non-profit entity organized under section 501(c)(4) of the U.S. Internal Revenue Code Churches Covered and Connected in Covenant, a religious association founded by Archbishop LeRoy Bailey Jr. Craiova Group a cooperation project of four European states – Romania, Bulgaria, Greece and Serbia – for the purposes of furthering their European integration as well as economic, transport and energy cooperation with one another. Sports C4 (classification), a Paralympic cycling classification C-4, professional wrestler Paul Burchill's name for his finishing move, a moonsault uranage C4, an abbreviation for a four-man Sprint Canoe, see Canoe racing C4, a term used to refer to the UEFA Intertoto Cup, a football competition (mainly used in non-English speaking countries) C4 level, a challenge square dance program at the Challenge 4 level Stationery C4, an international standard paper size (229 × 324 mm), defined in ISO 216 C4, the envelope size matching the A4 paper size Vehicles Aircraft C-4, the US Army designation of the Ford Trimotor AEG C.IV, a German World War I reconnaissance aircraft AGO C.IV, a 1917 German reconnaissance aircraft C-4 Academe, the military version of Gulfstream I twin turboprop business aircraft C-4 Argonaut, a Canadair aircraft derived from the Douglas DC-4 Cierva C.4, a 1922 Spanish experimental autogyro DFW C.IV, a 1916 German reconnaissance aircraft Flight Design C4, a four-seat light aircraft Fokker C.IV, a 1923 Dutch two-seat reconnaissance aircraft Rumpler C.IV, a 1917 German single-engine, two-seater reconnaissance biplane Automobiles C4, a class of Audi 100 and Audi A6 cars Chevrolet Corvette C4, the fourth production design of the Chevrolet Corvette Citroën C4, a car made by Citroën Coloni C4, a Formula One car built by Enzo Coloni Racing Car Systems Sauber C4, a Sauber sportscar Spyker C4, a Spyker car Locomotives Bavarian C IV, an 1884 German steam locomotive GS&WR Class C4, a Great Southern and Western Railway Irish steam locomotive LNER Class C4, a class of British steam locomotives Ships HMS C4, a British C class submarine of the Royal Navy Type C4 ship, merchant cargo ships of United States Maritime Commission "C" design USS C-4 (SS-15), a United States