psychiatrist vs specialist

psychiatrist and specialist both are nouns.

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

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

Other hypernyms of psychiatrist include medical specialist.

psychiatrist (noun)	specialist (noun)
a physician who specializes in psychiatry	an expert who is devoted to one occupation or branch of learning
	practices one branch of medicine