OK

"OK" (/oʊkeɪ/; also spelled "okay" or "ok") is an English word denoting approval, acceptance, agreement, assent, or acknowledgment. "OK" has frequently turned up as a loanword in many other languages and has been described as the world's most widely understood word.

As an adjective, "OK" principally means "adequate" or "acceptable" as a contrast to "bad" ("The boss approved this, so it is OK to send out"); it can also mean "mediocre" when used in contrast with "good" ("The french fries were great, but the burger was just OK"). It fulfills a similar role as an adverb ("Wow, you did OK for your first time skiing!"). As an interjection, it can denote compliance ("OK, I will do that"), or agreement ("OK, that is fine"). It can mean "assent" when it is used as a noun ("the boss gave his OK to the purchase") or, more colloquially, as a verb ("the boss OKed the purchase"). "OK", as an adjective, can express acknowledgment without approval. As a versatile discourse marker or back-channeling item, it can also be used with appropriate voice tone to show doubt or to seek confirmation ("OK?" or "Is that OK?").

Numerous explanations for the origin of the expression have been suggested, but few have been discussed seriously by linguists. The following proposals have found mainstream recognition.

The etymology that most reference works provide today is based on a survey of the word's early history in print: a series of six articles by Allen Walker Read, in the journal American Speech in 1963 and 1964. He tracked the spread and evolution of the word in American newspapers and other written documents, and later throughout the rest of the world. He also documented controversy surrounding OK and the history of its folk etymologies, both of which are intertwined with the history of the word itself. Read argues that, at the time of the expression's first appearance in print, a broader fad existed in the United States of "comical misspellings" and of forming and employing acronyms, themselves based on colloquial speech patterns:

...
Wikipedia