Poppy Day vs Great Britain

Poppy Day and Great Britain both are nouns.

Word	Noun	Adjective	Verb	Adverb
Poppy Day	Yes	No	No	No
Great Britain	Yes	No	No	No

Poppy Day (noun)	Great Britain (noun)
the Sunday nearest to November 11 when those who died in World War I and World War II are commemorated	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