tetrad vs quadruplet

tetrad and quadruplet both are nouns.

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

As nouns, tetrad and quadruplet are synonyms defined as:

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

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

tetrad (noun)	quadruplet (noun)
the cardinal number that is the sum of three and one	a set of four similar things considered as a unit
	one of four children born at the same time from the same pregnancy
	the cardinal number that is the sum of three and one