I have always wondered why some native speakers especially Americans start their sentences, even conversations with ok. Even here, some threads are started with OK. Correct me if I'm mistaken. The only way I know of starting a sentence with OK is when I am being asked a favor which I agree to grant. Examples: A: Could you please do this for me? B: OK, with pleasure. C: Come on please, please, please. D: OK. OK. OK. However, it seems like there is also an indiscriminate use of Ok as a sentence starter. Examples: OK. I started this thread because.... OK. You won't believe it but.... OK. Listen to me, I've got something to tell you... Can you please shed light on this matter? Thanks a lot.