[1] Application Development System

[2] Activity Data Sheet {Luftfahrt}

[3] Accurately Defined System

[4] Aitken Double Star catalogue - Katalog mit über 17000 Doppelsternen von Robert G. Aitken von 1932 (->"Penguin Dictionary of Astronomy")

[5] Astrophysics Data System (NASA/HAVARD)

[6] Automatic Distribution System

[7] Active Directory Service - proprietäres X.500 unter Windows NT (Microsoft, vergl. NDS)

[8] Advanced Digital System

[9] Audio Distribution System

[10] Auxilary Data System

[11] Dallas-Addison, TX, USA -internationale Fughafen-Kennung.