national capital vs capital of Sri Lanka

national capital and capital of Sri Lanka both are nouns.

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

national capital (noun)	capital of Sri Lanka (noun)
the capital city of a nation	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