Could have (done):
(1) When you do not really mean what you say:
- I was so tired. I could have slept for a week.
- When I saw the result I could have wept.( i.e I felt like weeping but I didn’t )
- I was so hungry. I could have eaten a horse.
- He behaved so stupidly. I was annoyed terribly. I could have beaten him.
(2) Most often we use ‘ Could have (done) ‘ for things which were possible but did not happen or past ability/permission unused.
- Why did you stay at a hotel when you went to Mumbai? You could have stayed with my brother. (i.e you had the opportunity to stay with him but you didn’t)
- Did you get to the top (of the mountain)?
- We could have done, but we didn’t try.
- Why did you walk? You could have taken my car.
- He fell of a ladder yesterday but he’s alright, he is lucky. He could have hurt himself badly.( But fortunately, he didn’t hurt himself)
- The situation was bad but it could have been worse.
(3) Could have (done) = would have been able to (do)
- Why didn’t you apply for the job? You could have got it.
- We could have gone away if we had had enough money.
- She couldn’t have gone away because she was ill. (= she wouldn’t have been able to go)
- You did very well to pass the exam. I am sure I couldn’t have been able to pass it if I had appeared for it.
- I don’t know how you worked so hard to achieve the target. I couldn’t have done it.