Eye

Definition
noun, plural: eyes
(1) The organ of sight or vision; the visual sense; the sense of seeing.
(2) A mark resembling the organ of sight in form, position or appearance, as the spot on the feather of a peacock or the spot on the wings of a butterfly, or the dark spot in a black-eyed pea.
(3) The scar to which the adductor muscle (or the adductor muscle itself) is attached in oysters and some bivalve shells.
(4) The bud or sprout of a plant or tuber, as the reproductive bud of a potato.
(5) The action of the organ of sight; view.
(6) The scope of vision.
(7) The center of a target.
Supplement
In man and most vertebrates, the eye pertains to the movable ball or globe in the orbit. However, most often the term includes the adjacent parts as well.
Eyes can see because the structure and function of these organs are specialized for detecting light and relaying electrical impulses along the optic nerve to the visual center of the brain.
The two major types of eyes based on structure are: simple eyes and compound eyes. Examples of simple eyes are pit eyes and pinhole eyes whereas compound eyes are superposition eyes and apposition eyes.
Word origin: From Middle English, from Old English ēaġe, from Common Germanic *augon, from Proto-Indo-European *h₃ekʷ- (“‘eye; to see’”).