gerontologist vs specialist

gerontologist and specialist both are nouns.

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

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

Other hypernyms of gerontologist include medical specialist.

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