noun proneness; tendency; as, the aptness of iron to rust.
2. aptness ·noun disposition of the mind; propensity; as, the aptness of men to follow example.
3. aptness ·noun fitness; suitableness; appropriateness; as, the aptness of things to their end.
4. aptness ·noun quickness of apprehension; readiness in learning; docility; as, an aptness to learn is more observable in some children than in others.