Disposition of the mind; propensity; as, the aptness of men to follow example.

Proneness; tendency; as, the aptness of iron to rust.

a disposition to behave in a certain way; "the aptness of iron to rust"; "the propensity of disease to spread"

Quickness of apprehension; readiness in learning; docility; as, an aptness to learn is more observable in some children than in others.

Fitness; suitableness; appropriateness; as, the aptness of things to their end.

appropriateness; "the phrase had considerable aptness"