folk vs stemma

folk and stemma both are nouns.

Word	Noun	Adjective	Verb	Adverb
folk	Yes	No	No	No
stemma	Yes	No	No	No

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

folk (noun)	stemma (noun)
the traditional and typically anonymous music that is an expression of the life of people in a community	an eye having a single lens
people in general (often used in the plural)	the hereditary derivation of an individual
a social division of (usually preliterate) people	a tree diagram showing a reconstruction of the transmission of manuscripts of a literary work
people descended from a common ancestor