internist vs specialist

internist and specialist both are nouns.

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

As nouns, specialist is a hypernym of internist; that is, specialist is a word with a broader meaning than internist:

Other hypernyms of internist include medical specialist.

internist (noun)	specialist (noun)
a specialist in internal medicine	an expert who is devoted to one occupation or branch of learning
	practices one branch of medicine