septenary vs sevener

septenary and sevener both are nouns.

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

As nouns, septenary and sevener are synonyms defined as:

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

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

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