apt 
(ăpt)
(ăpt)adj.
1. Exactly suitable; appropriate: an apt reply.
2. Having a natural tendency; inclined: She is apt to take offense easily. See Usage Note at liable.
3. Quick to learn or understand: an apt student.
[Middle English, from Old French apte, from Latin aptus, past participle of apere, to fasten.]
aptly adv.
aptness n.