- Ambiguous
- Ambitious
- Amblyopia
- Ambulatory
- Ameliorative
- Amorous
- Amortize
- Amperage
- Ampere
- Amplifier
- Amplify
- Amply
- Ampoule
- Amputate
- Amuck
- Amusement
- Anabolism
- Anacardium occidentale
- Anaemia
- Anaesthetist
- Analogous
- Analogy
- Analysable
- Analyse, analyze
- Anandavardhana
- Anarchism
- Anarchist
- Anasarca
- Anecdote
- Anemia
- Anencephalus
- Anent
- Anesthetic
- Anesthetist
- Aneurysms
- Anger
- Angina
- Angiras
- Anglicize
- Angling
- Anglo
- Anglophone
- Angora
- Angry
- Annihilated
- Annihilation
- Annualized
- Annuity
- Annus mirabilis
- Anodise
- Anomalous
- Anonym
- Anus
- Anterior
- Anther
- Anthrop
- Anthropocentric
- Anthropological
- Anthropologist
- Anti-revolutionary
- Anti-semitic
- Antibody
- Antic
- Antichrist
- Aphorism
- Apiculture
- Aplomb
- Apocalypse
- Apollo
- Apologetic
- Apologia
- Apologise
- Apologist
- Apophatic
- Apostacy
- Apostle
- Apothegm
- Appliance
- Application
- Applied mathematics
- Applied science
- Appositely
- Appositeness
- Apprehend
- Apprehension
- Apprehensively
- Apprise
- Apprize
- Approachable
- Approbate
- Approbatory
- Approve
- Approving
- April
- Apriori
- Apriorism
- Apropos
- Apse
- Arboured
- Arcanum