capital of the United States vs District of Columbia

capital of the United States and District of Columbia both are nouns.

Word	Noun	Adjective	Verb	Adverb
capital of the United States	Yes	No	No	No
District of Columbia	Yes	No	No	No

capital of the United States (noun)	District of Columbia (noun)
the capital of the United States in the District of Columbia and a tourist mecca; George Washington commissioned Charles L'Enfant to lay out the city in 1791	the district occupied entirely by the city of Washington; chosen by George Washington as the site of the capital of the United States and created out of land ceded by Maryland and Virginia