Athinai vs national capital

Athinai and national capital both are nouns.

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

Athinai (noun)	national capital (noun)
the capital and largest city of Greece; named after Athena (its patron goddess)	the capital city of a nation