national capital vs capital of Trinidad and Tobago

national capital and capital of Trinidad and Tobago both are nouns.

Word	Noun	Adjective	Verb	Adverb
national capital	Yes	No	No	No
capital of Trinidad and Tobago	Yes	No	No	No

national capital (noun)	capital of Trinidad and Tobago (noun)
the capital city of a nation	the capital and largest city of Trinidad and Tobago on the west coast of the island of Trinidad