Great Britain vs SAS

Great Britain and SAS both are nouns.

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

Great Britain (noun)	SAS (noun)
an island comprising England and Scotland and Wales	a specialist regiment of the British army that is trained in commando techniques of warfare and used in clandestine operations (especially against terrorist groups)
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