| Term | Definition |
| antithesis | an exact opposite |
| apathy | lack of feeling |
| ape | to mimic |
| aperture | an opening |
| apex | the highest point |
| aphasia | loss of the ability to speak |
| aphorism | brief saying |
| apiary | place where bees are kept |
| aplomb | self-confidence |
| apocryphal | not authentic |
| apogee | farthest point away from the earth |
| apoplexy | sudden loss of consciousness |
| apostate | one who gives up his beliefs |
| apothecary | druggist |
| apothegm | brief instructive saying |
| apotheosis | glorification of a person to the rank of God |
| appall | to frighten |
| apparel | clothing |
| apparition | a ghost |
| appease | to soothe |