- argil
- anthesis
- auxesis
- albuminoid
- acclimation
- acclimatization
- ammonia clock
- algebra
- anticyclone
- artemis
- alcoholic dementia
- arthritis
- apodictic
- Anabas
- agrarian
- arboriculture
- asafetida
- AIDS
- analog computer
- alimentary tract
- auricle
- arthropoda
- anal
- auriferous
- adventitia
- amphora
- activation
- allantois
- antistrophe
- allegorical
- anomia
- answerability
- apocrine gland
- ambiversion
- atomic mass unit
- anaglyph
- Anostraca
- Artiodactyla
- Acarina
- aftercare
- air thermometer
- athletic type
- architeuthis
- acumen
- acute gastritis
- arroyo
- analogist
- amity
- astride
- aesop