Great Britain vs u

Great Britain and u both are nouns.

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

Great Britain (noun)	u (noun)
an island comprising England and Scotland and Wales	the 21st letter of the Roman alphabet
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

Great Britain (adjective)	u (adjective)
	(chiefly British) of or appropriate to the upper classes especially in language use