simple eye vs stemma

simple eye and stemma both are nouns.

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

As nouns, simple eye and stemma are synonyms defined as:

Other synonyms of simple eye include ocellus.

simple eye (noun)	stemma (noun)
an eye having a single lens	an eye having a single lens
	the hereditary derivation of an individual
	a tree diagram showing a reconstruction of the transmission of manuscripts of a literary work