doctor vs allergist

doctor and allergist both are nouns.

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

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

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

doctor (verb)	allergist (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