OK vs indorsement

OK and indorsement both are nouns.

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

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

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

OK (noun)	indorsement (noun)
an endorsement	the act of endorsing
a state in south central United States	formal and explicit approval
	a promotional statement (as found on the dust jackets of books)
	a speech seconding a motion
	a signature that validates something

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