capital vs United Kingdom of Great Britain and Northern Ireland

capital and United Kingdom of Great Britain and Northern Ireland both are nouns.

Word	Noun	Adjective	Verb	Adverb
capital	Yes	Yes	No	No
United Kingdom of Great Britain and Northern Ireland	Yes	No	No	No

capital (noun)	United Kingdom of Great Britain and Northern Ireland (noun)
the upper part of a column that supports the entablature	a monarchy in northwestern Europe occupying most of the British Isles; divided into England and Scotland and Wales and Northern Ireland; `Great Britain' is often used loosely to refer to the United Kingdom
one of the large alphabetic characters used as the first letter in writing or printing proper names and sometimes for emphasis
a seat of government
a center that is associated more than any other with some activity or product
wealth in the form of money or property owned by a person or business and human resources of economic value
assets available for use in the production of further assets

capital (adjective)	United Kingdom of Great Britain and Northern Ireland (adjective)
of principal importance
first-rate
uppercase