United Kingdom of Great Britain and Northern Ireland vs police constable

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

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

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