doctor vs specialist

doctor and specialist both are nouns.

Word	Noun	Adjective	Verb	Adverb
doctor	Yes	No	Yes	No
specialist	Yes	No	No	No

As nouns, specialist is a hyponym of doctor; that is, specialist is a word with a more specific, narrower meaning than doctor:

doctor (noun)	specialist (noun)
children take the roles of physician or patient or nurse and pretend they are at the physician's office	an expert who is devoted to one occupation or branch of learning
a licensed medical practitioner	practices one branch of medicine
a person who holds Ph.D. degree (or the equivalent) from an academic institution

doctor (verb)	specialist (verb)
give medical treatment to
alter and make impure, as with the intention to deceive
restore by replacing a part or putting together what is torn or broken