Great Britain vs base rate

Great Britain and base rate both are nouns.

Word	Noun	Adjective	Verb	Adverb
Great Britain	Yes	No	No	No
base rate	Yes	No	No	No

Great Britain (noun)	base rate (noun)
an island comprising England and Scotland and Wales	the interest rate set by the Bank of England for lending to other banks
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