Western Church vs Roman Catholic Church

Western Church and Roman Catholic Church both are nouns.

Word	Noun	Adjective	Verb	Adverb
Western Church	Yes	No	No	No
Roman Catholic Church	Yes	No	No	No

As nouns, Western Church and Roman Catholic Church are synonyms defined as:

Western Church and Roman Catholic Church: the Christian Church based in the Vatican and presided over by a pope and an episcopal hierarchy

Other synonyms of Western Church include Church of Rome, Roman Catholic, Roman Church.

Western Church (noun)	Roman Catholic Church (noun)
the Christian Church based in the Vatican and presided over by a pope and an episcopal hierarchy	the Christian Church based in the Vatican and presided over by a pope and an episcopal hierarchy