county town vs United Kingdom of Great Britain and Northern Ireland

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

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

county town (noun)	United Kingdom of Great Britain and Northern Ireland (noun)
the town or city that is the seat of government for a county	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