quaternary vs quadruplet

quaternary and quadruplet both are nouns.

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

As nouns, quaternary and quadruplet are synonyms defined as:

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

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

quaternary (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

quaternary (adjective)	quadruplet (adjective)
consisting of or especially arranged in sets of four
coming next after the third and just before the fifth in position or time or degree or magnitude