foursome vs quartet

foursome and quartet both are nouns.

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

As nouns, foursome and quartet are synonyms defined as:

Other synonyms of foursome include quartette.

As nouns, foursome and quartet are synonyms defined as:

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

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

foursome (noun)	quartet (noun)
four people considered as a unit	a musical composition for four performers
the cardinal number that is the sum of three and one	four people considered as a unit
	a set of four similar things considered as a unit
	four performers or singers who perform together
	the cardinal number that is the sum of three and one