foursome vs quaternity

foursome and quaternity both are nouns.

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

As nouns, foursome and quaternity are synonyms defined as:

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

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

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