mamma's boy vs boy

mamma's boy and boy both are nouns.

Word	Noun	Adjective	Verb	Adverb
mamma's boy	Yes	No	No	No
boy	Yes	No	No	No

As nouns, boy is a hypernym of mamma's boy; that is, boy is a word with a broader meaning than mamma's boy:

mamma's boy: a boy excessively attached to his mother; lacking normal masculine interests
boy: a male human offspring

Other hypernyms of mamma's boy include son.

mamma's boy (noun)	boy (noun)
a boy excessively attached to his mother; lacking normal masculine interests	a youthful male person
	(ethnic slur) offensive and disparaging term for Black man
	a friendly informal reference to a grown man
	a male human offspring