capital of Norway vs national capital

capital of Norway and national capital both are nouns.

Word	Noun	Adjective	Verb	Adverb
capital of Norway	Yes	No	No	No
national capital	Yes	No	No	No

capital of Norway (noun)	national capital (noun)
the capital and largest city of Norway; the country's main port; located at the head of a fjord on Norway's southern coast	the capital city of a nation