eye vs simple eye

eye and simple eye both are nouns.

Word	Noun	Adjective	Verb	Adverb
eye	Yes	No	Yes	No
simple eye	Yes	No	No	No

As nouns, simple eye is a hyponym of eye; that is, simple eye is a word with a more specific, narrower meaning than eye:

Other hyponyms of eye include naked eye, peeper, oculus dexter, OD, oculus sinister, OS, ocellus, stemma, compound eye.

eye (noun)	simple eye (noun)
a small hole or loop (as in a needle)	an eye having a single lens
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

eye (verb)	simple eye (verb)
look at