Meaning

• Used to indicate acknowledgement or acceptance.

  "I promise to give it back. – OK."

• Used to introduce a sentence in order to draw attention to the importance of what is being said.

  "OK, I'm thinking of a number…"

• Used in turn-taking, serving as a request to the speaker to grant the turn to the interrupter.

  "You always do this to me! When we were at your mother’s, you said that… – OK, OK, …"