quaternity vs foursome

quaternity and foursome both are nouns.

Word	Noun	Adjective	Verb	Adverb
quaternity	Yes	No	No	No
foursome	Yes	No	No	No

As nouns, quaternity and foursome are synonyms defined as:

quaternity and foursome: the cardinal number that is the sum of three and one

Other synonyms of quaternity include 4, four, IV, Little Joe, quadruplet, quartet, quatern, quaternary, quaternion, tetrad.

quaternity (noun)	foursome (noun)
the cardinal number that is the sum of three and one	four people considered as a unit
	the cardinal number that is the sum of three and one