paediatrician vs specialist

paediatrician and specialist both are nouns.

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

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

Other hypernyms of paediatrician include medical specialist.

paediatrician (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