• a musical note, the A below Middle C
• A3, a German rocket design during World War II
• Alabama 3, a band known as A3 in the U.S. to avoid confusion with the country group Alabama
• The IATA code for Aegean Airways
• Audi A3, a model of automobile
• HLA-A3 is a Human MHC Serotype HLA-A
• HMS A3, a British A class submarine of the Royal Navy
• USS Grampus (SS-4), a Plunger class submarine of the United States Navy
• In town and country planning in the United Kingdom, A3 is the code for permission to use specific land or premises for restaurants and cafés
• LNER Class A1/A3 a Pacific Locomotive Designed by Sir Nigel Gresley
• The A3 Air Operations Branch of the UK Joint Force Air Component Hedquaters
• The A3 Champions Cup, a club football tournamant also known as the East Asian Champions Cup
• "Anytime, anywhere, anyplace" an SMS abbreviation
• %A3 is the Url Encoded version of the Pound symbol (£).
• Proyect A3, as a Massive Multiplayer Online Role Player Game MMORPG
• Airbus A300

  A-3

  The variant A-3 can refer to:
  
• A-3 Falcon an attack aircraft manufactured by the Curtiss Aircraft Company
• A-3 Skywarrior, a strategic bomber manufactured by Douglas Aircraft Company
• Abrial A-3 Oricou, a French touring aircraft designed in 1927
• Alpha Trion, as the former name of this character from the Transformers Series
• ARITH-MATIC, as the former name for this programming language

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