OK vs USA

OK and USA both are nouns.

Word	Noun	Adjective	Verb	Adverb
OK	Yes	No	No	Yes
USA	Yes	No	No	No

OK (noun)	USA (noun)
an endorsement	the army of the United States of America; the agency that organizes and trains soldiers for land warfare
a state in south central United States	North American republic containing 50 states - 48 conterminous states in North America plus Alaska in northwest North America and the Hawaiian Islands in the Pacific Ocean; achieved independence in 1776

OK (adverb)	USA (adverb)
an expression of agreement normally occurring at the beginning of a sentence