- Antique
- Apheresis
- Aplasia
- Aplenty
- Apocalyptic
- Apolitical
- Apologue
- Apoplectic
- Apostatize
- Apostrophe
- Apotheosis
- Applicable
- Application window
- Applicator
- Appointed
- Appointed time
- Apposite
- Apposition
- Appraisal
- Appraised
- Appreciation
- Aptitude
- Aptness
- Aqua
- Aquamarine
- Aquaphobia
- Aquarius
- Aquatic
- Aqueous
- Aquifer
- Arabia
- Arabic
- Arak
- Arbitrary
- Arbor
- Arcot
- Arcturus
- Are
- Area code
- Arena
- Areola
- Argania
- Argon
- Armoury
- Armpit hair
- Arms race
- Army
- Arouses
- Arrack
- Arras
- Array
- Arraying
- Arrear
- Arrive
- Arrogance
- As free as air
- As helpless as a babe
- As i see it
- As it comes
- As it stands
- As keen as mustard
- As large as life
- As many
- As matter of
- As much as possible
- As of
- Ascending
- Ascending node of caput draconis
- Ascii
- Ascription
- Aseity
- Asepsis
- Ash
- Ash wednesday
- Ash-gourd
- Ask for a blank cheque
- Ask for the moon
- Assembling
- Assertion
- Assessment
- Assets
- Assignation
- Assignee
- Assimilation
- Assist in
- Associates
- Association
- Astrogeology
- Astroid
- Astrologers
- Astronaut
- Astrophysicist
- Asvamedha sacrifice
- Asymmetrical
- Asymptote
- At a loose end
- At a price
- At a run
- At one leisure
- At one's fingertips