quartet vs quadruplet

quartet and quadruplet both are nouns.

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

As nouns, quartet and quadruplet are synonyms defined as:

quartet and quadruplet: a set of four similar things considered as a unit

Other synonyms of quartet include quadruple, quartette.

As nouns, quartet and quadruplet are synonyms defined as:

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

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

quartet (noun)	quadruplet (noun)
a musical composition for four performers	a set of four similar things considered as a unit
four people considered as a unit	one of four children born at the same time from the same pregnancy
a set of four similar things considered as a unit	the cardinal number that is the sum of three and one
four performers or singers who perform together
the cardinal number that is the sum of three and one