United Kingdom of Great Britain and Northern Ireland vs Security Service

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

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

United Kingdom of Great Britain and Northern Ireland (noun)	Security Service (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 government agency in the United Kingdom that is responsible for internal security and counterintelligence on British territory