nigga vs Black

nigga and Black both are nouns.

Word	Noun	Adjective	Verb	Adverb
nigga	Yes	No	No	No
Black	Yes	No	No	No

As nouns, Black is a hypernym of nigga; that is, Black is a word with a broader meaning than nigga:

nigga: (ethnic slur) extremely offensive name for a Black person
Black: a person with African ancestry, "Negro" and "Negroid" are archaic and pejorative today

Other hypernyms of nigga include African-American, Negro, Negroid, Black person, blackamoor.

nigga (noun)	Black (noun)
(ethnic slur) extremely offensive name for a Black person	a person with African ancestry, "Negro" and "Negroid" are archaic and pejorative today
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	British chemist who identified carbon dioxide and who formulated the concepts of specific heat and latent heat (1728-1799)