| A | B |
| a capella | singing without instrumental accompaniment |
| Accolade | award, honour or laudatory notice |
| Acme | from the Greek akme, highest point |
| Adagio | slower than andante but faster than larghetto |
| Addendum | a thing to be added, plural: addenda |
| Ad hoc | Latin: for this purpose |
| Ad Hominem | argumentum ad hominem: to change the subject |
| Adieu | fond farewell, French: a dieu to God |
| Ad Infinitum | Latin: infinity or endlessly |
| Adobe | building material from sand, clay, straw, bricks dried in the sun |
| Aftermath | originally a second crop of grass |
| Agnostic | asserting the uncertainty of all claims to knowledge |
| Agony | extreme prolonged pain |
| Altruism | unselfish concern for the welfare of others |
| Ambrosia | favoured food of the gods |
| Ampersand | & |
| Anathema | a person or thing detested |
| Antimacassar | protective covering for the backs of chairs |
| Arrant | downright, thorough, notorious |
| Agony | extreme, prolonged pain |