aptness

Suitability; the quality of being apt or suitable.

A regular supply of coking slack is sent from Durham to the Scunthorpe area, in view of its special aptness for steelmaking processes, [...].

Disposition of the mind; propensity.

the aptness of men to follow example

Speed or readiness in learning; docility.

An aptness to learn is more observable in some children than in others.

Proneness; tendency.

the aptness of iron to rust