OK

Concise Oxford English Dictionary © 2008 Oxford University Press:
OK1 (also okay) informal

▶exclamation

• 1 expressing agreement or acquiescence.

• 2 introducing an utterance.

▶adjective

• 1 satisfactory; fairly good.

• 2 permissible.

▶adverb in a satisfactory manner or to a satisfactory extent. ▶noun an authorization or approval. ▶verb (OK's, OK'ing, OK'd) give approval to.

word history: The exclamation OK is first recorded in the mid 19th century. It is most probably an abbreviation of orl korrect, a humorous form of all correct, which was popularized as a slogan during US President Martin Van Buren's re-election campaign of 1840. The initials also represented his nickname Old Kinderhook, derived from his birthplace, Kinderhook in New York State.

Concise Oxford English Dictionary © 2008 Oxford University Press:
OK2

▶abbreviation Oklahoma (in official postal use).