- Apparition
- Appear
- Appellate
- Appendage
- Appendix
- Apperception
- Appetising
- Appetitive
- Appetizing
- Apple
- Applet
- Appleton layer
- Appreciator
- Apprehensive
- Apprenticed
- Appress
- Approaching
- Approching
- Appropriate
- Approval
- Approximately
- Approximation
- Apricot
- Apt
- 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
- Articles of association
- Articulated
- Artillary
- Artilleryman
- Artiodactyl
- Artocarpus heterophyllus
- Artocarpus hirstula
- Arundhati star
- As a result of
- 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