sevener vs septet

sevener and septet both are nouns.

Word	Noun	Adjective	Verb	Adverb
sevener	Yes	No	No	No
septet	Yes	No	No	No

As nouns, sevener and septet are synonyms defined as:

Other synonyms of sevener include 7, heptad, septenary, seven, VII.

sevener (noun)	septet (noun)
the cardinal number that is the sum of six and one	a musical composition written for seven performers
	seven people considered as a unit
	a set of seven similar things considered as a unit
	seven performers or singers who perform together
	the cardinal number that is the sum of six and one