archpriest vs hierarch

archpriest and hierarch both are nouns.

Word	Noun	Adjective	Verb	Adverb
archpriest	Yes	No	No	No
hierarch	Yes	No	No	No

As nouns, archpriest and hierarch are synonyms defined as:

Other synonyms of archpriest include high priest, prelate, primate.

archpriest (noun)	hierarch (noun)
a senior clergyman and dignitary	a senior clergyman and dignitary
	a person who holds a high position in a hierarchy