A4 commonly refers to:
A4 paper, a paper size defined by the ISO 216 standard, measuring
A4 and variants may also refer to:
Arts and media A4 or A4, the musical note La or A in the fourth octave A440 (pitch standard), the use of the musical note A to reference musical pitch A4, a 1981 component for the Scourge of the Slave Lord adventure in the Dungeons and Dragons role playing game Vlad A4, Belarusian YouTuber
Military units A4, the designation for air force headquarters in the NATO continental staff system concerned with logistics A4 Air Logistics, a branch of the Joint Force Air Component Headquarters in the UK A 4; see List of Swedish regiments for A4, a Swedish designation (4th Artillery Regiment) that has been used by: Gotland Artillery Regiment (designation: A 4), until 1892 Norrland Artillery Regiment (designation: A 4), 1893–1997
Science and technology Computing Apple A4, a microprocessor used in some Apple products AMD A4, a microprocessor Samsung Galaxy A04, a smartphone manufactured by Samsung Electronics
Biology and medicine ATC code A04 Antiemetics and antinauseants, a subgroup of the Anatomical Therapeutic Chemical Classification System Lipoxin A4, a lipoxin Androstenedione, an androgen steroid hormone Combretastatin A-4, a stilbenoid chemical compound Subfamily A4, a rhodopsin-like receptors subfamily
Other uses in science and technology
British NVC community A4 (Hydrocharis morsus-ranae - Stratiotes aloides community), one type of Aquatic communities in the British National Vegetation Classification system A4, the alternating group on four elements A4, a type of stainless steel Lely (company) Astronaut A4, the fourth version of the Astronaut robot manufactured by Lely Zeolite A-4, a sodium-type molecular sieve also known as 4A M16A4, a variant of the American M16 rifle
Transportation Aeronautics and astronautics A-4 Helldiver, the civil version of the Curtiss Falcon an attack aircraft manufactured by Curtiss Aircraft Company Douglas A-4 Skyhawk, a 1954 attack aircraft manufactured by Douglas Aircraft Company Breda A.4, a 1926 Italian biplane trainer aircraft Aggregat-4, the technical name for V-2 ballistic missile Southern Winds Airlines (IATA code: A4), a defunct Argentine airline Azimuth (airline) (IATA code: A4), a Russian airline A-004, the sixth and final abort test of the Apollo spacecraft SPAD S.A-4, 1915 French reconnaissance fighter built by SPAD
Railways Bavarian A IV, an 1852 German steam locomotive model LNER Class A4, a class of steam locomotives, including the famous Mallard PRR A4, an American Pennsylvania Railroad locomotive classification Togoshi Station (station number A-04), Toei Asakusa Line, Tokyo
Ships USS A-4 (SS-5), a Plunger-class submarine of the US Navy HMNZS Kahu (A04), a 1978 Royal New Zealand Navy Moa-class inshore patrol vessel HMS A4, an A-class submarine of the Royal Navy Belgian ship A4, a Belgian naval patrol vessel of World War II
Other vehicles Audi A4, a luxury compact executive car manufactured by Audi, introduced in 1994 Arrows A4, a 1982 British racing car Prussian A 4, a Prussian railbus Leopard 1A4, a variant of the German Leopard 1 main battle tank Leopard 2A4, a variant of the German Leopard 2 main battle tank
Roads and routes List of A4 roads A4, a Metrobus route in Washington, D.C., US
Other uses A4 paper, a paper size defined by the ISO 216 standard, measuring A4 (classification), an amputee sport classification Réti Opening (Encyclopaedia of Chess Openings code: A04) A4, a climbing route grade In town and country planning in the UK, code A4, permission to use specific land or premises for pubs and bars A4 pod, a family of killer whales living in British Columbia coastal waters Biu-Mandara A.4 languages, a family of languages spoken in Cameroon and Nigeria A4 Revolution, the 2022 COVID-19 protests in China Assembly Four, an Australian computer technology company which operated Switter
See also 4A (disambiguation) A4A (disambiguation) AIV (disambiguation)