lad vs fellow

lad and fellow both are nouns.

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

As nouns, lad and fellow are synonyms defined as:

Other synonyms of lad include blighter, bloke, chap, cuss, fella, feller, gent.

lad (noun)	fellow (noun)
a male child (a familiar term of address to a boy)	a boy or man
a boy or man	a man who is the lover of a man or woman
	a friend who is frequently in the company of another
	a person who is member of one's class or profession
	an informal form of address for a man
	a member of a learned society
	one of a pair