the ability to understand quickly and clearly

ability to understand and reason

the state of being very bright

genius

(showing) ability to deceive easily

devious

the power to reason (contrasted with emotions and instinct)

capability of the mind; someone with capable mind

the power to learn, understand and know; information, especially with reference to important events

ability to perceive, understand

Intelligence Quotient (a measure for comparing intelligence)

ability to perceive, understand

the ability (from training and practice) to do something well

ability, talent to do something

(an example of) natural ability (to do something well)

ability