altar boy vs male child

altar boy and male child both are nouns.

Word	Noun	Adjective	Verb	Adverb
altar boy	Yes	No	No	No
male child	Yes	No	No	No

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

Other hypernyms of altar boy include acolyte, boy.

altar boy (noun)	male child (noun)
a boy serving as an acolyte	a youthful male person