Great Britain vs island

Great Britain and island both are nouns.

Word	Noun	Adjective	Verb	Adverb
Great Britain	Yes	No	No	No
island	Yes	No	No	No

Great Britain (noun)	island (noun)
an island comprising England and Scotland and Wales	a zone or area resembling an island
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	a land mass (smaller than a continent) that is surrounded by water