United Kingdom of Great Britain and Northern Ireland vs mere

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

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

United Kingdom of Great Britain and Northern Ireland (noun)	mere (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 small pond of standing water

United Kingdom of Great Britain and Northern Ireland (adjective)	mere (adjective)
	apart from anything else; without additions or modifications
	being nothing more than specified