male child vs boy

male child and boy both are nouns.

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

As nouns, male child and boy are synonyms defined as:

male child (noun)	boy (noun)
a youthful male person	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