Baku vs national capital

Baku and national capital both are nouns.

Word	Noun	Adjective	Verb	Adverb
Baku	Yes	No	No	No
national capital	Yes	No	No	No

Baku (noun)	national capital (noun)
a port city on the Caspian Sea that is the capital of Azerbaijan and an important center for oil production	the capital city of a nation