Solway Firth vs Great Britain

Solway Firth and Great Britain both are nouns.

Word	Noun	Adjective	Verb	Adverb
Solway Firth	Yes	No	No	No
Great Britain	Yes	No	No	No

Solway Firth (noun)	Great Britain (noun)
a large firth on the west coast of Britain between England and Scotland	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