heptad vs sevener

heptad and sevener both are nouns.

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

As nouns, heptad and sevener are synonyms defined as:

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

heptad (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