The ability to think and understand readily and quickly; quick-wittedness, alertness; mental dexterity; (also) an instance of this.

Capacity, comprehension.

Mental power or capacity; cleverness, astuteness. In later use also: academic aptitude.

figurative. Mental equipment or qualification; capacity; plural abilities, faculties, powers (of mind). Obsolete.

Active power or force of mind; mental ability, talent.