boy vs lad

boy and lad both are nouns.

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

As nouns, lad is a hyponym of boy; that is, lad is a word with a more specific, narrower meaning than boy:

boy (noun)	lad (noun)
a youthful male person	a male child (a familiar term of address to a boy)
(ethnic slur) offensive and disparaging term for Black man	a boy or man
a friendly informal reference to a grown man
a male human offspring