- Aspects
- Aspersion
- Assafoetida
- Assail
- Assam
- Assassinate
- Assault
- Assay
- 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
- Attendant
- Attending
- Attentive
- Attestation
- Attractiveness
- Atwitter
- Au courant
- 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
- Adp
- Airily
- A bad pill to swallow
- A bed of roses
- A bird in hand is worth two in the bush
- A bit much
- A blood relative
- A cardinal error
- A dead duck
- A dead luck
- A dear john letter
- A man of few words
- A man of mark
- A matter of fact
- A matter of life and death
- A measure of
- A milk-n-honey drink
- A narrow escape
- A nasty one
- A near death experience
- A needle in a haystack
- A penny for your thoughts
- A pep talk
- A stay of some length
- A sweet-meat
- A tight fit
- A variety of aloe-wood
- A vaunt
- A wandering jew
- A web of lies
- A white lie