Great Britain vs point duty

Great Britain and point duty both are nouns.

Word	Noun	Adjective	Verb	Adverb
Great Britain	Yes	No	No	No
point duty	Yes	No	No	No

Great Britain (noun)	point duty (noun)
an island comprising England and Scotland and Wales	the control of traffic by a policeman stationed at an intersection
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