capital of Northern Ireland vs Northern Ireland

capital of Northern Ireland and Northern Ireland both are nouns.

Word	Noun	Adjective	Verb	Adverb
capital of Northern Ireland	Yes	No	No	No
Northern Ireland	Yes	No	No	No

capital of Northern Ireland (noun)	Northern Ireland (noun)
capital and largest city of Northern Ireland; the center of Protestantism in Northern Ireland	a division of the United Kingdom located on the northern part of the island of Ireland