- 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
- Anonymous letter
- Anorexic
- Another key
- Answer back to
- Answer for
- Antechamber
- Antennae
- Antepenultimate
- Anticipation
- Anticipative
- Antihelmintic
- Antihistamines
- Antilog
- Antilogarithm
- Antimacassar
- Antinomy
- Antiquity
- Antithesis
- Antithetical
- Antitype
- Antral gastritis
- Aphorism
- Apiculture
- Aplomb
- Apocalypse
- Apollo
- Apologetic
- Apologia
- Apologise
- Apologist
- Apophatic
- Apostacy
- Apostle
- Apothegm
- Appliance
- Application
- Applied mathematics
- Applied science
- Appositely
- Appositeness
- Arboured
- Arcanum
- Arch
- Arch-work
- Archaeological
- Archaeology
- Archaic
- Archaism
- Archbishopric
- Archeology
- Archipelago
- Architecter
- Architecture
- Aright
- Aril
- Arithmetically
- Arithmetician