Apt"ness, n.
1.
Fitness; suitableness; appropriateness; as, the aptness of things to their end.
The aptness of his quotations.
J. R. Green.
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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.
© Webster 1913.