La locución okay, también escrita OK u O.K. indica afirmación y proviene del inglés estadounidense. En inglés, también se usa como adjetivo y adverbio.
La primera vez que aparecen las siglas o.k. es el 23 de marzo de 1839 en el periódico "Boston Morning Post" cuya autoría es atribuida a su editor Charles Gordon Greene en el siguiente texto:
The above is from the Providence Journal, the editor of which is a little too quick on the trigger, on this occasion. We said not a word about our deputation passing "through the city" of Providence.—We said our brethren were going to New York in the Richmond, and they did go, as per Post of Thursday. The "Chairman of the Committee on Charity Lecture Bells", is one of the deputation, and perhaps if he should return to Boston, via Providence, he of the Journal, and his train-band, would have his "contribution box," et ceteras, o.k.—all correct—and cause the corks to fly, like sparks, upward.