- At peak
- At play
- At sea
- At sixes and sevens
- At stake
- At the eleventh hour
- At the longest
- At the same time
- At the top of ones voice
- 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
- Attendant
- Attending
- Attentive
- Attestation
- Attractiveness
- Atwitter
- Au courant
- Auctioneer
- Audibility
- Audibleness
- Audibly
- Audit
- Audition
- Auditor
- Aught
- Augmented reality
- August-september
- Augustly
- Aunt
- Aureate
- Aurora
- Auster
- Austere
- Auteur
- Authenticate
- Authentication
- Authorised
- Authoritarianism
- Authoritative
- Authorized person
- Autistic
- Auto index
- Auto-ignition
- Autobiography
- Autodidact
- Automatism
- Autoradiograph
- Autosomal chromosome
- Autotrophic
- Auxiliary bishop
- Availability
- Available resources
- Avarice
- Avenue
- Averse
- Aviation
- Aviatrix
- Aviculture
- Await
- Awaiting
- Awake to
- Awake to reality
- Awareness
- Awash
- Awful
- Awkward age
- Awl
- Ax
- Axe helve
- Axiom
- Axiomatic
- Axis neutral
- Axle
- Ayodhya
- Azoic
- Absolvable
- Air
- Altaltissimo
- Ark