quartet vs four

quartet and four both are nouns.

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

As nouns, quartet and four are synonyms defined as:

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

quartet (noun)	four (noun)
a musical composition for four performers	a playing card or domino or die whose upward face shows four pips
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
the cardinal number that is the sum of three and one

quartet (adjective)	four (adjective)
	being one more than three