lad vs sonny boy

lad and sonny boy both are nouns.

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

As nouns, lad and sonny boy are synonyms defined as:

Other synonyms of lad include cub, laddie, sonny.

lad (noun)	sonny boy (noun)
a male child (a familiar term of address to a boy)	a male child (a familiar term of address to a boy)
a boy or man