"OK" and "It’s OK" are opposite

When it comes to saying no and declining offers, lots of people say, “It’s okay”, or “I’m okay.” This means "no", and says that the present situation is fine and there is no need for change.  

    A: Would you like a plastic bag?
    B: It’s OK. I’ll just put it in my handbag.

On the other hand, if you say, "OK", that means "yes".

    A: Would you like a plastic bag?
    B: OK. Thank you.

But often in my lessons, this will happen:

    Me: So, should we look at the textbook now?
    Student: It’s OK.
    Me: So, yes or no?

As a teacher, I know that students confuse "OK" and "It's OK", so I understand that we should probably look at the textbook. My student is trying to say, "OK. Let's look at the book."

However, a native English speaker who isn't used to talking with non-native speakers could understand this as a negative: "No, thank you. I'd rather do something different today."

What the student should have said was simply, "OK".

This can be confusing, so most native speakers clear it up by adding additional positive or negative information:

  •     Positive: "OK, sure"; "Yea, OK"; "OK, fine"; or "OK. Sounds good."
  •     Negative: "No, it’s OK"; "Actually, I’m OK"; "I’m OK, thanks"; or "It's OK, thanks."

Also worth noting is that the tone is very different:

  •     "It’s OK"/"I’m OK": Here the first word should be long and the tone should go down at the end.
  •     OK: This should be said very short and the tone should go up.

If this seems strange, consider the fact that 大丈夫 can be either positive or negative in the same way.

Try it out in your next lesson!