Great Britain vs carriageway

Great Britain and carriageway both are nouns.

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

Great Britain (noun)	carriageway (noun)
an island comprising England and Scotland and Wales	one of the two sides of a motorway where traffic travels in one direction only usually in two or three lanes
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