pteridologist vs expert

pteridologist and expert both are nouns.

Word	Noun	Adjective	Verb	Adverb
pteridologist	Yes	No	No	No
expert	Yes	Yes	No	No

As nouns, expert is a hypernym of pteridologist; that is, expert is a word with a broader meaning than pteridologist:

pteridologist (noun)	expert (noun)
an expert in the study of ferns	a person with special knowledge or ability who performs skillfully

pteridologist (adjective)	expert (adjective)
	having or showing knowledge and skill and aptitude
	of or relating to or requiring special knowledge to be understood