mixed-blood vs quadroon

mixed-blood and quadroon both are nouns.

Word	Noun	Adjective	Verb	Adverb
mixed-blood	Yes	No	No	No
quadroon	Yes	No	No	No

As nouns, quadroon is a hyponym of mixed-blood; that is, quadroon is a word with a more specific, narrower meaning than mixed-blood:

mixed-blood: a person whose ancestors belonged to two or more racial groups
quadroon: an offspring of a mulatto and a white parent; a person who is one-quarter black

Other hyponyms of mixed-blood include mulatto, octoroon, half-caste, Metis.

mixed-blood (noun)	quadroon (noun)
a person whose ancestors belonged to two or more racial groups	an offspring of a mulatto and a white parent; a person who is one-quarter black