baby vs lover

baby and lover both are nouns.

Word	Noun	Adjective	Verb	Adverb
baby	Yes	No	Yes	No
lover	Yes	No	No	No

As nouns, lover is a hypernym of baby; that is, lover is a word with a broader meaning than baby:

baby (noun)	lover (noun)
a project of personal concern to someone	a person who loves someone or is loved by someone
a very young mammal	an ardent follower and admirer
a very young child (birth to 1 year) who has not yet begun to walk or talk	a significant other to whom you are not related by marriage
the youngest member of a group (not necessarily young)
an immature childish person
an unborn child; a human fetus
a beloved person; used as terms of endearment

baby (verb)	lover (verb)
treat with excessive indulgence