- a mythical being with human figures and a head of horse or with a horse's body and the head of a man
- annus mirabilis
- anterior serratus muscle
- anal sphincter
- alla breve
- american mink
- atypical pneumonia
- acute myelocytic leukemia
- acute myeloid leukemia
- a text_book
- Aquilegia vulgaris
- Aquilegia scopulorum calcarea
- Aquilegia caerulea
- a large mythological eagle_like bird believed to be the vehicle of lord vishṉū
- audio quality
- audio response
- A_list
- and so
- and then
- artist's workroom
- as against
- a notice
- an address
- addressability measure
- addressable position
- addressable register
- addlebrained
- addressable storage
- addressable horizontal position
- addressable point
- address computation
- address comparator
- address resolution
- aldebaran
- alpha orionis
- apres ski
- aldose
- alpha angle
- aldolase
- antiknock
- arterial angioma
- alveolar carcinoma
- alveolabial sulcus
- alveolar adenocarcinoma
- alveolar abscess
- alveolar angle
- alveolar air
- alveolar analgesic
- according
- arteria alveolaris superior