capital of Turkmenistan vs national capital

capital of Turkmenistan and national capital both are nouns.

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

capital of Turkmenistan (noun)	national capital (noun)
the capital and largest city of Turkmenistan	the capital city of a nation