Great Britain vs invigilator

Great Britain and invigilator both are nouns.

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

Great Britain (noun)	invigilator (noun)
an island comprising England and Scotland and Wales	someone who watches examination candidates to prevent cheating
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