high priest vs archpriest

high priest and archpriest both are nouns.

Word	Noun	Adjective	Verb	Adverb
high priest	Yes	No	No	No
archpriest	Yes	No	No	No

As nouns, high priest and archpriest are synonyms defined as:

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

high priest (noun)	archpriest (noun)
a senior clergyman and dignitary	a senior clergyman and dignitary
a preeminent authority or major proponent of a movement or doctrine