Special Air Service vs Great Britain

Special Air Service and Great Britain both are nouns.

Word	Noun	Adjective	Verb	Adverb
Special Air Service	Yes	No	No	No
Great Britain	Yes	No	No	No

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