tree diagram vs stemma

tree diagram and stemma both are nouns.

Word	Noun	Adjective	Verb	Adverb
tree diagram	Yes	No	No	No
stemma	Yes	No	No	No

As nouns, stemma is a hyponym of tree diagram; that is, stemma is a word with a more specific, narrower meaning than tree diagram:

tree diagram: a figure that branches from a single root
stemma: a tree diagram showing a reconstruction of the transmission of manuscripts of a literary work

Other hyponyms of tree diagram include cladogram.

tree diagram (noun)	stemma (noun)
a figure that branches from a single root	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