ball boy vs boy

ball boy and boy both are nouns.

Word	Noun	Adjective	Verb	Adverb
ball boy	Yes	No	No	No
boy	Yes	No	No	No

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

Other hypernyms of ball boy include male child.

ball boy (noun)	boy (noun)
a boy who retrieves balls for tennis players	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