Great Britain vs Special Branch

Great Britain and Special Branch both are nouns.

Word	Noun	Adjective	Verb	Adverb
Great Britain	Yes	No	No	No
Special Branch	Yes	No	No	No

Great Britain (noun)	Special Branch (noun)
an island comprising England and Scotland and Wales	a government police department dealing with political security
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