1. An inherent ability, as for learning; a talent: an aptitude for mathematics. See synonyms at ability.
2. Archaic. The condition or quality of being suitable; appropriateness.

[Middle English, tendency, from Late Latin aptitūdō, aptitude, from Latin aptus, apt. See apt.]

The American Heritage® Dictionary of the English Language, Fourth Edition Copyright © 2007, 2000 by Houghton Mifflin Company. Updated in 2009. Published by Houghton Mifflin Company. All rights reserved.