- (anthropology) Initialism of Australian Anthropological Society.
- (arachnology) Initialism of American Arachnological Society (a society of amateur and professional arachnologists)
- (astronautics) Initialism of American Astronautical Society (an independent scientific and technical group in the United States)
- (astronomy) Initialism of American Astronomical Society (a United States society of professional astronomers)
- (Australia, sciences) Initialism of Australian Academy of Science (an independent, government-endorsed society with the aim of promoting science)
- (aviation) Initialism of Advanced Automation System. (radarcontrol of transoceanic air corridors)
- (biotechnology) Initialism of All-America Selections (an organization that promotes development of new garden seed varieties)
- (geometry) Initialism of Angle-Angle-Side triangular congruency.
- (health) Initialism of Air Ambulance Service (a UK charity)
- (help) Initialism of Assyrian Aid Society.
- (human rights) Initialism of American Anti-Slavery Society.
- (politics) Initialism of Ansar al-Sunna (or Jamaat Ansar al-Sunna, a militant group operating in Iraq)
- (medicine, psychology) Initialism of American Association of Suicidology (an American nonprofit suicide prevention organization)
- (medicine) Initialism of Association for Academic Surgery.
- (military) Initialism of Arnold Air Society (a professional honorary service organization for Air Force officer candidates)
- (physics) Initialism of Atomic Absorption Spectroscopy.
- (research) Initialism of American Antiquarian Society (an American society and national research library)
- (research) Initialism of Association for Asian Studies.
- (research) Initialism of Assyrian Academic Society.
- (sciences) Initialism of African Academy of Sciences (an Africa-wide scientific organization)