I'm confused when I have to write "Ok" in a writing, because I don't know if "OK" and "Ok" are both orthographically correct or just one is.

  • 2
    I would think to be pedantically correct you would either write 'OK', the abbreviation for okay (or for the US state Oklahoma), or the full word 'okay'. However, OK is informal, and I think it's fairly common to write it either way (OK or ok). I wouldn't write Ok unless it was the start of a sentence.
    – ColleenV
    May 21, 2016 at 17:14
  • In English it's Okay or OK (sometimes O.K.). In Italian it is a loan word from English and is written Ok. That's fine if they are writing in Italian. But when they write in English, I ask native Italian speakers and other non-native speakers of English to correct it to Okay or OK because I assume they want to write the way English speakers do. May 21, 2016 at 18:14

2 Answers 2


OK is the abbreviation for oll korrect or orl korrect representing all correct. There are numerous explanations for the origin of the expression as suggested by the linked Wikipedia article.

You don't write Usa or USa for USA because USA is the abbreviation for the United States of America.

However, there are many forms of abbreviations in English and there is no hard-and-fast rule. For example, you abbreviate mister to Mr. or Mr and Doctor of Philosophy to PhD.

You could write Ok or ok in a text message or informal writing, but you should use one of the following three in formal writing. I would prefer OK to O.K..




  • 2
    +1 because I am constantly telling learners that in English it is OK or Okay and not Ok. However, there is some first language interference, for in Italian the norm is Ok, which is "Okay by me," since Italian speakers can decide how they want to write it–in Italian. A side issue is that Mister is shortened to Mr in British English. May 21, 2016 at 18:10
  • "Okay" is the expansion of OK, not the other way around. OK is an abbreviation of "oll korrect," not "okay." "Okay" came later.
    – amaranth
    May 21, 2016 at 21:16
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    @anaranjada: That's not right. The word (in whatever spelling you like) was originally borrowed from Choctaw. The "oll korrect" joke-interpretation came later. (See web.archive.org/web/20120208134453/http://…; hat-tip to english.stackexchange.com/a/60686/14775.) Unfortunately, the mistake has made it into some highly-regarded dictionaries.
    – ruakh
    May 21, 2016 at 21:52
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    @ruakh: The etymology seems unclear, considering other answers on that page. Rathony, I think it might be better to say something like "OK may have originated as an abbreviation of oll correct" to reflect this uncertainty.
    – sumelic
    May 21, 2016 at 22:01
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    @ruakh I don't think the etymology is all that clear. There seems to be a lack of documentation supporting most theories, as OED mentions. etymonline.com/index.php?term=OK c2.com/cgi/wiki?EtymologyOfOkay
    – ColleenV
    May 22, 2016 at 3:25

The important thing to understand is:

     OK is written as if it were an an acronym even though it doesn't stand for anything but itself.

So, the common practice in print is to write OK or O.K. or okay but not Ok.

There are various hypotheses about the origin of OK, like "oll korrect" (a joke misspelling for "all correct") or "Old Kinderhook" (a nickname of Martin Van Buren), but few people have heard of those things, and really, nobody knows. The origin of OK doesn't matter, because when people use the word today, they are not invoking an ongoing tradition in which the letters stand for something other than the spoken word "okay".

Some people say that OK stands for "okay" in the same way that IOU (as a noun, as in "I'll give you an IOU for $6") stands for the phrase "I owe you". As a theory of the origin of OK, that's probably wrong. But it correctly explains how the word OK communicates today and why it's customary to write it with two capital letters. When people write "IOU", they expect the reader to understand that the letters stand for "I owe you" because the names of the letters sound the same as the words. When people write "OK", they do not expect the reader to understand that the letters stand for "oll korrect". They do expect the reader to understand it as meaning "okay", which is pronounced the same as the letters "OK".

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