- 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
- At ones last gasp
- At ones own pace
- At that
- Atomic theory
- Atomic warfare
- Atomic weight
- Atoms
- Atomy
- Atony
- Atriculate
- Attach
- Attack
- Attacked
- Attained puberty
- Aubade
- Auberage
- Aubergine
- Aubum hair
- Auction
- Auctionary
- Audience
- Audio
- Audio-visual aids
- Auditory ossicles
- Augean stables
- Augmentation
- Augur
- Augury
- Authoritatively
- Authority
- Authorization
- Authorized
- Autism
- Auto-typography
- Autochthons
- Autocrat
- Autograph
- Automatic dictionary
- Automatic pagination
- Automatism
- Autoradiograph
- Autosomal chromosome
- Autotrophic
- Auxiliary bishop
- Availability
- Available resources
- Avarice
- Avenue
- Averse
- Aviation
- Aviatrix
- Aviculture
- Axiomatic
- Axis neutral
- Axle
- Ayodhya
- Azoic
- Absolutist
- Aero
- A
- A bad patch
- A bed of thorn
- A big name
- A bird in the hand is worth two in the bush
- A bit thick
- A capital offence
- A caste title
- A cheat
- A chip of the old block
- A confirmed bachelor
- A cross-breed of male horse and female deer
- A mad dash
- A mad scramble
- A man of senses
- A matter of course
- A medicinal herb
- A medicinal plant
- A momant
- A musical drum
- A pair
- A peg to hang on