third eyelid vs eye

third eyelid and eye both are nouns.

Word	Noun	Adjective	Verb	Adverb
third eyelid	Yes	No	No	No
eye	Yes	No	Yes	No

third eyelid (noun)	eye (noun)
a protective fold of skin in the eyes of reptiles and birds and some mammals	a small hole or loop (as in a needle)
	the organ of sight
	good discernment (either visually or as if visually)
	attention to what is seen
	an area that is approximately central within some larger region

third eyelid (verb)	eye (verb)
	look at