police constable vs United Kingdom of Great Britain and Northern Ireland

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

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

police constable (noun)	United Kingdom of Great Britain and Northern Ireland (noun)
a police officer of the lowest rank	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