1. actionable - Affording cause for instituting an action, as trespass, slanderous words.
2. actuality - Any reality.
3. actuary - An officer, as of an insurance company, who calculates and states the risks and premiums.
4. actuate - To move or incite to action.
5. acumen - Quickness of intellectual insight, or discernment; keenness of discrimination.
6. acute - Having fine and penetrating discernment.
7. adamant - Any substance of exceeding hardness or impenetrability.
8. addendum - Something added, or to be added.
9. addle - To make inefficient or worthless; muddle.
10. adduce - To bring forward or name for consideration.
11. adhere - To stick fast or together.
12. adherence - Attachment.
13. adherent - Clinging or sticking fast.
14. adhesion - The state of being attached or joined.
15. adieu (inter) - Good-by; farewell.