(1):

(n.) The faculty of perceiving; the faculty, or peculiar part, of man's constitution by which he has knowledge through the medium or instrumentality of the bodily organs; the act of apperhending material objects or qualities through the senses; - distinguished from conception.

(2):

(n.) The quality, state, or capability, of being affected by something external; sensation; sensibility.

(3):

(n.) An idea; a notion.

(4):

(n.) The act of perceiving; cognizance by the senses or intellect; apperhension by the bodily organs, or by the mind, of what is presented to them; discernment; apperhension; cognition.