quartette vs foursome

quartette and foursome both are nouns.

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

As nouns, quartette and foursome are synonyms defined as:

Other synonyms of quartette include quartet.

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