Great Britain vs plain flour

Great Britain and plain flour both are nouns.

Word	Noun	Adjective	Verb	Adverb
Great Britain	Yes	No	No	No
plain flour	Yes	No	No	No

Great Britain (noun)	plain flour (noun)
an island comprising England and Scotland and Wales	flour that does not contain a raising agent
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