One idiom that can be very confusing for ESL students learning English is OK. Specifically, does OK mean “yes” or “no”?
Most of the time OK means “yes” or that something is acceptable:
Do you want to watch a movie tonight? OK (yes, that’s acceptable)
Would you like chicken or beef for dinner? Chicken is OK. (I choose chicken. Chicken is acceptable.)
Sometimes OK is used to mean that something is good enough or average.
Did you like the movie? It could have been better, but it was OK. (The movie was not great, but also not bad.)
How did you do on the test? I thought the exam was very hard, but I did OK. (I did not do well on the exam, but I did not fail it either.)
Sometimes OK is used to mean safe or healthy.
Last week she was very sick, but she is OK now. (She is feeling healthy again.)
I heard you were in a car accident. Are you OK? (Did you get hurt?)
Finally, “That’s OK” is often used to politely refuse a request. It means the same thing, as “No, thank you.” This is the only time that OK has a negative meaning. “That’s all right” is also used this way.
Do you want to watch a movie tonight? OK. (Yes, accepting)
Do you want to watch a movie tonight? That’s OK. (No, polite refusal)
Can I help you carry your luggage? All right. (Yes, accepting)
Can I help you carry your luggage? That’s all right, it’s not heavy. (No, polite refusal)
There are a few other situations when we use OK, but that’s all for now.