OK vs countenance

OK and countenance both are nouns.

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

As nouns, countenance is a hypernym of OK; that is, countenance is a word with a broader meaning than OK:

Other hypernyms of OK include endorsement, imprimatur, indorsement, sanction, warrant.

OK (noun)	countenance (noun)
an endorsement	the appearance conveyed by a person's face
a state in south central United States	the human face (`kisser' and `smiler' and `mug' are informal terms for `face' and `phiz' is British)
	formal and explicit approval

OK (verb)	countenance (verb)
	consent to, give permission; permit

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