stemma vs tree diagram

stemma and tree diagram both are nouns.

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

As nouns, tree diagram is a hypernym of stemma; that is, tree diagram is a word with a broader meaning than stemma:

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

Other hypernyms of stemma include tree.

stemma (noun)	tree diagram (noun)
an eye having a single lens	a figure that branches from a single root
the hereditary derivation of an individual
a tree diagram showing a reconstruction of the transmission of manuscripts of a literary work