octonary vs ogdoad

octonary and ogdoad both are nouns.

Word	Noun	Adjective	Verb	Adverb
octonary	Yes	No	No	No
ogdoad	Yes	No	No	No

As nouns, octonary and ogdoad are synonyms defined as:

octonary and ogdoad: the cardinal number that is the sum of seven and one

Other synonyms of octonary include 8, eight, eighter, eighter from Decatur, octad, octet, VIII.

octonary (noun)	ogdoad (noun)
the cardinal number that is the sum of seven and one	the cardinal number that is the sum of seven and one