- Arbitress
- Archive
- Archives
- Archivist
- Ardent
- Arduous
- Area manager
- Areal flood
- Aren't
- Argent
- Arguing
- Argumentation
- Arms
- Army corps
- Aroma
- Aromatic
- Arpeggio
- Arrange
- Arrest
- Arrest attention
- Arrhythmic
- Arrived
- As clear as mud
- As far as possible
- As fit as a fiddle
- As if
- As memory serves
- As much again
- As old as methuselah
- Ascendent
- Asceticism
- Asecrtained
- Asexuality
- Ash-colour
- Ashore
- Ashy
- Asian palm civet
- Aside
- Ask for
- Assured
- Asthenia
- 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
- Auctioneer
- Audibility
- Audibleness
- Audibly
- Audit
- Audition
- Auditor
- Aught
- Augmented reality
- August-september
- Augustly
- Authorized person
- Autistic
- Auto index
- Auto-ignition
- Autobiography
- Autodidact
- Automation
- Autonomy
- Axle-tree
- Azolla
- Azure
- Adp
- Airily
- Amaranthus
- Antiquary
- Auctor
- A disciple who lodges with his preceptor
- A divine ministrel
- A dogs life
- A dry
- A false alarm
- A fiche
- A fish