capital of Egypt vs national capital

capital of Egypt and national capital both are nouns.

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

capital of Egypt (noun)	national capital (noun)
the capital of Egypt and the largest city in Africa; a major port just to the south of the Nile delta; formerly the home of the Pharaohs	the capital city of a nation