Negress vs Negro

Negress and Negro both are nouns.

Word	Noun	Adjective	Verb	Adverb
Negress	Yes	No	No	No
Negro	Yes	No	No	No

As nouns, Negro is a hypernym of Negress; that is, Negro is a word with a broader meaning than Negress:

Negress: a Black woman or girl
Negro: a person with African ancestry, "Negro" and "Negroid" are archaic and pejorative today

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

Negress (noun)	Negro (noun)
a Black woman or girl	a person with African ancestry, "Negro" and "Negroid" are archaic and pejorative today