national capital vs Addis Ababa

national capital and Addis Ababa both are nouns.

Word	Noun	Adjective	Verb	Adverb
national capital	Yes	No	No	No
Addis Ababa	Yes	No	No	No

national capital (noun)	Addis Ababa (noun)
the capital city of a nation	the capital of Ethiopia and the country's largest city; located in central Ethiopia