Okay, OK, and O.K. are all acceptable spellings of the word. OK is more common in edited writing, but okay appears about a third of the time. O.K. is preferred by a few publications, including the New York Times, even though it is not an abbreviation of anything in modern use.
The word has several main uses. As an adjective, it’s synonymous with acceptable, passable, or good. Something that is OK is positive, but not as positive as it could be. It also works as an interjection used to express agreement or approval. From this extends its verb sense, to agree or approve, and from the verb extends its noun sense, agreement or approval.
There are many theories about the origins of the word, some more plausible than others. The Oxford English Dictionary and the Chambers Dictionary of Etymology agree that it’s apparently an early-19th-century American abbreviation of oll korrect, a jocular misspeling of all correct. Other theories are that the word somehow came from Old Kinderhook, the nickname of U.S. president Martin Van Buren; that it has Native American origins; that it was a Morse code abbreviation; and that it is an abbreviation of out of kash, another jocular misspelling (for out of cash).
OK, maybe it’s not there yet. [Wall Street Journal]
OK, so what myths are we talking about? [Guardian]
It might be OK for a beefy Wallaby to stare down a bunch of powerfully built Kiwis as they launch into a ferocious, blood-curdling haka. [Sydney Morning Herald]
Okay, okay, I’ll stop right there. [The Star-Ledger]
FDA okays Thermo Fisher test to help kidney transplant [Reuters]
We’ve done O.K. in the downturn because we started selling online in 2007. [New York Times]