What does aptness mean?
The definition of aptness
Apt”ness, n.
1 Fitness; suitableness; appropriateness; as, the aptness of things to their end. The aptness of his quotations. J. R. Green.
2 Disposition of the mind; propensity; as, the aptness of men to follow example.
3 Quickness of apprehension; readiness in learning; docility; as, an aptness to learn is more observable in some children than in others.
4 Proneness; tendency; as, the aptness of iron to rust.