“Are you feeling OK? [= well]” “Yes, I'm fine.” Don't worry. Everything will be OK. [= all right] “I'm so sorry that I'm late.” “It's/That's OK. We still have plenty of time.” “Are you OK for money?” “Yes, I have enough.” He seems like an okay [= decent] guy. The boss needs to OK this before we place the order. Who OK'd your request? More @Wikipedia
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