all-mains vs U.K.

all-mains is not a noun while U.K. is a noun.

Word	Noun	Adjective	Verb	Adverb
all-mains	No	Yes	No	No
U.K.	Yes	No	No	No

all-mains (noun)	U.K. (noun)
	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

all-mains (adjective)	U.K. (adjective)
used of a radio receiver that is adaptable to all voltages