tetrad vs foursome

tetrad and foursome both are nouns.

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

As nouns, tetrad and foursome are synonyms defined as:

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

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

tetrad (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