copper's nark vs Great Britain

copper's nark and Great Britain both are nouns.

Word	Noun	Adjective	Verb	Adverb
copper's nark	Yes	No	No	No
Great Britain	Yes	No	No	No

copper's nark (noun)	Great Britain (noun)
an informer or spy working for the police	an island comprising England and Scotland and Wales
	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