O.K. vs countenance

O.K. and countenance both are nouns.

Word	Noun	Adjective	Verb	Adverb
O.K.	Yes	No	Yes	Yes
countenance	Yes	No	Yes	No

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

Other hypernyms of O.K. include endorsement, imprimatur, indorsement, sanction, warrant.

O.K. (noun)	countenance (noun)
an endorsement	the appearance conveyed by a person's face
	the human face (`kisser' and `smiler' and `mug' are informal terms for `face' and `phiz' is British)
	formal and explicit approval

O.K. (verb)	countenance (verb)
give sanction to	consent to, give permission; permit

O.K. (adverb)	countenance (adverb)
in a satisfactory or adequate manner