ap·ti·tude 
(ăptĭ-td′, -tyd′)
(ăptĭ-td′, -tyd′)n.
1. An inherent ability, as for learning; a talent: an aptitude for mathematics.
2. Archaic The condition or quality of being suitable; appropriateness.
[Middle English, tendency, from Late Latin aptitūdō, aptitude, from Latin aptus, apt; see APT.]
ap′ti·tudi·nal (-tdn-əl, -tyd-) adj.
ap′ti·tudi·nal·ly adv.