Holy Father vs Vicar of Christ

Holy Father and Vicar of Christ both are nouns.

Word	Noun	Adjective	Verb	Adverb
Holy Father	Yes	No	No	No
Vicar of Christ	Yes	No	No	No

As nouns, Holy Father and Vicar of Christ are synonyms defined as:

Other synonyms of Holy Father include Bishop of Rome, Catholic Pope, pontiff, pope, Roman Catholic Pope.

Holy Father (noun)	Vicar of Christ (noun)
the head of the Roman Catholic Church	the head of the Roman Catholic Church