doctor vs care for

doctor is a noun but care for is not a noun.

Word	Noun	Adjective	Verb	Adverb
doctor	Yes	No	Yes	No
care for	No	No	Yes	No

As verbs, care for is a hypernym of doctor; that is, care for is a word with a broader meaning than doctor:

Other hypernyms of doctor include treat.

doctor (noun)	care for (noun)
children take the roles of physician or patient or nurse and pretend they are at the physician's office
a licensed medical practitioner
a person who holds Ph.D. degree (or the equivalent) from an academic institution

doctor (verb)	care for (verb)
give medical treatment to	provide treatment for
alter and make impure, as with the intention to deceive	have a liking, fondness, or taste (for)
restore by replacing a part or putting together what is torn or broken	be fond of; be attached to