UK vs IR

UK and IR both are nouns.

Word	Noun	Adjective	Verb	Adverb
UK	Yes	No	No	No
IR	Yes	No	No	No

UK (noun)	IR (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	a board of the British government that administers and collects major direct taxes