- Approached
- Approbation
- April fool
- Aptly
- Aqua regia
- Aquaculture
- Arab
- Arabian jasmine
- Arbiter
- Arbitral
- Arboreal
- Arcade
- Arch-enemy
- Archaeologically
- Archaically
- Archangel
- Archduke
- Arched
- Archers
- Archetype
- Archie
- Arching
- Architect of gods
- Architrave
- Archivolt
- Archon
- Ardor
- Ardour
- Argentine
- Argosy
- Arguable
- Argue
- Argus
- Arid
- Arise
- Arisen
- Aristocracy
- Arithmetic
- Arithmetic progression
- Arithmetical progression
- Armada
- Armadillo
- Armature
- Armchair
- Armed
- Armed neutrality
- Armenius
- Armhole
- Armoire
- Armour
- Armour-plated
- Aromatherapy
- Arose
- Arouse
- Aroused
- Arpanet
- Arraign
- Arrangement
- Arrayed
- Arrestable
- Arrogant person
- Arrogantly
- Arrow-root plant
- Arrowhead
- Arrowroot
- Arsenal
- Arsonist
- Art of war
- Artefact
- Artful
- Article
- Articleship
- Artifice
- Artificial
- Artificial intelligence
- As opposed to
- Artificial satellite
- Artillery
- Artisan
- Artisans
- Arty
- Arum
- Aruna
- As a matter of fact
- As a rule
- As common as much
- As common as muck
- As cool as a cucumber
- As far as
- As far as i know
- As far as one can tell
- As far as one is concerned
- As flat as a pancake
- As for
- As good as new
- As long as
- As many again
- As one likes
- As per
- As plain as the nose