national capital vs Praha

national capital and Praha both are nouns.

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

national capital (noun)	Praha (noun)
the capital city of a nation	the capital and largest city of the Czech Republic in the western part of the country; a cultural and commercial center since the 14th century