capital of Sri Lanka vs national capital

capital of Sri Lanka and national capital both are nouns.

Word	Noun	Adjective	Verb	Adverb
capital of Sri Lanka	Yes	No	No	No
national capital	Yes	No	No	No

capital of Sri Lanka (noun)	national capital (noun)
the capital and largest city of Sri Lanka; has one of the largest harbors in the world; is located on the western coast of the island of Ceylon	the capital city of a nation