- Achy
- Acid test
- Acidity
- Acknowledgement
- Acknowledgment
- Acolyte
- Acoustics
- Acquaintances
- Act up to
- Acting
- Actinic
- Actinotherapy
- Action plan
- Actions
- Actions speak louder than words
- Activation
- Active and passive voices
- Activex
- Add to
- Addenda
- Additionally
- Address size
- Adenoids
- Adept
- Adequacy
- Administratively
- Administrator
- Admirably
- Admiralty
- Admire for
- Admired
- Admissible
- Admittedly
- Admix
- Admonish
- Adolescence
- Adopted
- Adorable
- Adoration
- Adventurer
- Adventures
- Adventurous
- Adversarial
- Adversity
- Advertise
- Advisors
- Advocacy
- Adze
- Aegis
- Aeon
- Aeration
- Affectionately
- Affinity with (for, between)
- Affix
- Affluenza
- Affright
- Affront
- Affronted by
- Aggressive
- Agitator
- Aglow
- Agog
- Agonising
- Agonizingly
- Agree
- Agree to
- Agree with
- Agreeably
- Air frieght
- Air rifle
- Air service
- Air speed
- Air-conditioning
- Air-cushion
- Air-sea rescue
- Air-to-air
- Airbus
- Aircraft carrier
- Aircraftman
- Alas
- Alas!
- Albion
- Alcoholism
- Alcove
- Ale
- Alexander
- Alga
- Algonquin
- All over
- All person
- All right
- All star
- All such
- All the way
- All time
- All-pervading
- All-purpose
- All-wise
- Allayment
- Amatory