pediatrician vs specialist

pediatrician and specialist both are nouns.

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

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

Other hypernyms of pediatrician include medical specialist.

pediatrician (noun)	specialist (noun)
a specialist in the care of babies	an expert who is devoted to one occupation or branch of learning
	practices one branch of medicine