(1):
(n.) Proneness; tendency; as, the aptness of iron to rust.
(2):
(n.) Quickness of apprehension; readiness in learning; docility; as, an aptness to learn is more observable in some children than in others.
(3):
(n.) Disposition of the mind; propensity; as, the aptness of men to follow example.
(4):
(n.) Fitness; suitableness; appropriateness; as, the aptness of things to their end.