quadruplet vs quaternity

quadruplet and quaternity both are nouns.

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

As nouns, quadruplet and quaternity are synonyms defined as:

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

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

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