sibling vs quad

sibling and quad both are nouns.

Word	Noun	Adjective	Verb	Adverb
sibling	Yes	No	No	No
quad	Yes	No	No	No

As nouns, quad is a hyponym of sibling; that is, quad is a word with a more specific, narrower meaning than sibling:

Other hyponyms of sibling include half blood, quadruplet, quin, quint, quintuplet, triplet, twin.

sibling (noun)	quad (noun)
a person's brother or sister	a rectangular area surrounded on all sides by buildings
	(printing) a block of type without a raised letter; used for spacing between words or sentences
	a muscle of the thigh that extends the leg
	one of four children born at the same time from the same pregnancy