boy vs Black man

boy and Black man both are nouns.

Word	Noun	Adjective	Verb	Adverb
boy	Yes	No	No	No
Black man	Yes	No	No	No

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

boy (noun)	Black man (noun)
a youthful male person	a man who is Black
(ethnic slur) offensive and disparaging term for Black man
a friendly informal reference to a grown man
a male human offspring