- a disposition to behave in a certain way; "the aptness of iron to rust"; "the propensity of disease to spread"
- appropriateness for the occasion; "the phrase had considerable aptness"
- Fitness; suitableness; appropriateness; as, the aptness of things to their end; Disposition of the mind; propensity; as, the aptness of men to follow example; Quickness of apprehension; readiness in learning; docility; as, an aptness to learn is more observable in some children than in others; ...