- Appleton layer
- Appreciator
- Apprehensive
- Apprenticed
- Appress
- Approaching
- Approching
- Appropriate
- Approval
- Approximately
- Approximation
- Apricot
- Apt
- Arboretum
- Arcane
- Arch-rival
- Archaeologist
- Archbishop
- Archery
- Architecturally
- Arian
- Aries
- Aristocrat
- Aristocratic
- Arithmetical
- Armed guard
- Armed to the teeth
- Armistice
- Arrow-tip
- Art of arms
- Art of dancing
- Art paper
- Artefactual
- Artery
- Arthritis
- Artichoke
- Artichokes
- Articles of association
- Articulated
- Artillary
- Artilleryman
- Artiodactyl
- Artocarpus heterophyllus
- Artocarpus hirstula
- Arundhati star
- As a result of
- As per rule
- As poor as a church mouse
- As silent as a grave
- As well as
- As-much-as-one-can-do
- Asbestos
- Ascc
- Askance
- Asmall box of chunna
- Asoka forest
- Asokatree
- Aspen
- Aspergillum
- Asperse
- Aspirant
- Aspirin
- Assegai
- Association of ideas
- Assurance
- Assuredly
- Astern
- Astonish
- Astonishing
- Astonishingly
- Astounded
- Astounding
- Astraphobia
- Astride
- At a stroke
- At all
- At any cost
- At any moment
- At every turn
- At first light
- At first sight
- At great length
- At least
- At most
- At night
- At odds
- At one leisure
- At one's fingertips
- At ones last gasp
- At ones own pace
- At that
- Atomic theory
- Atomic warfare
- Atomic weight
- Atoms
- Atomy
- Atony
- Atriculate
- Attach
- Attack