Eternal City vs Roman

Eternal City and Roman both are nouns.

Word	Noun	Adjective	Verb	Adverb
Eternal City	Yes	No	No	No
Roman	Yes	Yes	No	No

Eternal City (noun)	Roman (noun)
capital and largest city of Italy; on the Tiber; seat of the Roman Catholic Church; formerly the capital of the Roman Republic and the Roman Empire	a resident of modern Rome
	an inhabitant of the ancient Roman Empire

Eternal City (adjective)	Roman (adjective)
	of or relating to or supporting Romanism
	of or relating to or derived from Rome (especially ancient Rome)
	characteristic of the modern type that most directly represents the type used in ancient Roman inscriptions