foursome vs quartette

foursome and quartette both are nouns.

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

As nouns, foursome and quartette are synonyms defined as:

Other synonyms of foursome include quartet.

foursome (noun)	quartette (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