United Kingdom of Great Britain and Northern Ireland vs returning officer

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

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

United Kingdom of Great Britain and Northern Ireland (noun)	returning officer (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	the official in each electorate who holds the election and returns the results