lambkin vs lamb

lambkin and lamb both are nouns.

Word	Noun	Adjective	Verb	Adverb
lambkin	Yes	No	No	No
lamb	Yes	No	Yes	No

As nouns, lamb is a hypernym of lambkin; that is, lamb is a word with a broader meaning than lambkin:

lambkin (noun)	lamb (noun)
a very young lamb	young sheep
	the flesh of a young domestic sheep eaten as food
	a sweet innocent mild-mannered person (especially a child)
	a person easily deceived or cheated (especially in financial matters)

lambkin (verb)	lamb (verb)
	give birth to a lamb