- Astis
- Astonished
- Astraddle
- Astral body
- Astray
- At all costs
- At all times
- At close quarters
- At dawn
- At full pelt
- At full strain
- At hand
- At knife point
- At length
- At will
- Atelophobia
- Atheism
- Atheistic
- Athri
- Athwart
- Atlantic
- Atmosphere
- Atom
- Atomic
- Atomic number
- Atone
- Atonement
- Atrocious
- Atrocities
- Atrorcious
- Attaching
- Attachment
- Attachments
- Attacker
- Attain
- Attempt the impossible
- Auctioneer
- Audibility
- Audibleness
- Audibly
- Audit
- Audition
- Auditor
- Aught
- Augmented reality
- August-september
- Augustly
- Authorized person
- Autistic
- Auto index
- Auto-ignition
- Autobiography
- Autodidact
- Automation
- Autonomy
- Avionics
- Awake
- Awe
- Awe-inspiring
- Awestruck
- Awhile
- Awkwardly
- Awn
- Axle-tree
- Azolla
- Azure
- Adhatoda vasica
- Adherent
- Adiabatic
- Adieu
- Adipose
- Aditya
- Adjourn
- Adjutant
- Angst
- Angular
- Angular diameter
- Aniconism
- Animal kingdom
- Animistic
- Anise seed
- Anise seed herb
- Annexe
- Another
- Anothers wife
- Ansi
- Antagonize
- Antarctic
- Ante
- Anvil
- Anticipatory
- Anticyclone
- Antifoundationalism
- Antihero
- Antilogy
- Antimycotic
- Antinational
- Antique
- Apheresis
- Aplasia