United Kingdom of Great Britain and Northern Ireland vs second estate

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

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

United Kingdom of Great Britain and Northern Ireland (noun)	second estate (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 nobility in France and the peerage in Britain