| adversary | one's opponent in a contest, conflict, or dispute | |
| adulterate | To render (something) poorer in quality by adding another substance, typically an inferior one | |
| adulation | Excessive admiration or praise | |
| adroit | very skillful and quick in the way one thinks or moves | |
| adorned | Make more beautiful or attractive | |
| admonish | Warn or reprimand someone firmly | |
| adhere | To stick fast or cleave, as a glutinous substance does; to become attached or united | |
| adequate | Sufficient for a specific requirement; enough | |
| adept | Very skilled or proficient at something | |
| adamant | Refusing to be persuaded or to change one's mind | |