- 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 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
- A pinch of
- A pipe-dream
- Axilla
- Absurd
- Absurdism
- Absurdity
- Abundantly
- Abused
- Abutting
- Abysmal
- Ac
- Acc
- Accelerated
- Acceleration
- Accompanist
- Accord
- According as
- Accountancy
- Accountant
- Accoutre
- Accoutrement
- Accreditation
- Acquaintanceship
- Acquiesce
- Acquisitive
- Acquittal
- Acre
- Acrimonious
- Acrobatic
- Acrobatics
- Acropolis
- Across
- Act of grace
- Act upon
- Actinomorphy
- Action
- Actionable
- Actionable claim
- Activator
- Active
- Activist
- Activities
- Actors
- Actove movie
- Actuarial
- Actuary
- Actuate
- Acuate
- Acupuncture
- Ad hoc
- Ad infinitum
- Adamantine
- Adapt
- Adapter
- Add fuel to the fire
- Add insult to injury
- Add operator
- Addict
- Addition
- Additive month
- Address bus
- Address oneself to
- Addressing
- Adherents
- Adhesion
- Adhesive
- Adios