Great Britain vs guest night

Great Britain and guest night both are nouns.

Word	Noun	Adjective	Verb	Adverb
Great Britain	Yes	No	No	No
guest night	Yes	No	No	No

Great Britain (noun)	guest night (noun)
an island comprising England and Scotland and Wales	an evening when members of a club or college can bring their friends as guests
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