sevener vs septenary

sevener and septenary both are nouns.

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

As nouns, sevener and septenary are synonyms defined as:

sevener and septenary: the cardinal number that is the sum of six and one

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

sevener (noun)	septenary (noun)
the cardinal number that is the sum of six and one	the cardinal number that is the sum of six and one