high priest vs hierarch

high priest and hierarch both are nouns.

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

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

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

high priest (noun)	hierarch (noun)
a senior clergyman and dignitary	a senior clergyman and dignitary
a preeminent authority or major proponent of a movement or doctrine	a person who holds a high position in a hierarchy