Bishop of Rome vs Leo the Great

Bishop of Rome and Leo the Great both are nouns.

Word	Noun	Adjective	Verb	Adverb
Bishop of Rome	Yes	No	No	No
Leo the Great	Yes	No	No	No

Bishop of Rome (noun)	Leo the Great (noun)
the head of the Roman Catholic Church	Italian pope from 400 to 461 who extended the authority of the papacy to the west and persuaded Attila not to attack Rome (400-461)