descent vs sept

descent and sept both are nouns.

Word	Noun	Adjective	Verb	Adverb
descent	Yes	No	No	No
sept	Yes	No	No	No

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

Other hyponyms of descent include family, family line, folk, kinfolk, kinsfolk, phratry, side, breed line.

descent (noun)	sept (noun)
the act of changing your location in a downward direction	people descended from a common ancestor
properties attributable to your ancestry
a movement downward
the hereditary derivation of an individual
a downward slope or bend
the kinship relation between an individual and the individual's progenitors