Great Britain vs caster sugar

Great Britain and caster sugar both are nouns.

Word	Noun	Adjective	Verb	Adverb
Great Britain	Yes	No	No	No
caster sugar	Yes	No	No	No

Great Britain (noun)	caster sugar (noun)
an island comprising England and Scotland and Wales	very finely granulated sugar that was formerly sprinkled from a castor
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