| Term | Definition |
| apex | the highest point |
| apostate | one who renounces religious faith |
| apothecary | early form of pharmacist |
| appall | to cause one to feel shock or disapproval |
| apprehensible | capable of being conceived |
| approbation | approval |
| arbitrate | to mediate |
| arbor | tree |
| ardent | showing strong emotion |
| ardor | intense feeling of love |
| arraign | to bring before a court to face charges |
| arrogate | to claim or take without right |
| ascent | slope |
| ascetic | practicing self-denial |
| asperity | harshness of manner |
| assent | to agree or express agreement |
| assiduous | diligent |
| assimilate | to adapt |
| astringent | Harsh in disposition or character. |
| astute | clever |
| atone | make amends for |
| audacious | fearless |
| austere | severely simple |
| avarice | greedy |
| avidity | eagerness |