Great Britain vs speech day

Great Britain and speech day both are nouns.

Word	Noun	Adjective	Verb	Adverb
Great Britain	Yes	No	No	No
speech day	Yes	No	No	No

Great Britain (noun)	speech day (noun)
an island comprising England and Scotland and Wales	an annual day in the schools when speeches are made and prizes are distributed
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