Rule Explanation Example
"Could" is used as the past form of - I can hear something. (now) → I
Could as the past of can
"can." could hear something. (past)
"Could" is used for possible actions
Could for possible - What shall we do tonight? → We
now or in the future, especially to
actions or suggestions could go to the cinema.
make suggestions.
Could for unrealistic "Could" (not "can") is used for - I’m so tired, I could sleep for a week.
actions actions that are unrealistic. (not "I can sleep for a week")
"Could" (not "can") is used to
Could for possibilities in - The story could be true, but I don’t
express possibilities now or in the
the present or future think it is. (not "can be true")
future.
"Could have" is used to talk about
Could have (done) for - Why did you stay at a hotel? You
past possibilities that did not
past possibilities could have stayed with me.
happen.
Couldn’t do something - I couldn’t live in a big city. I’d hate it.
"Couldn’t" means something is or
(impossible now or in (now) - I couldn’t run yesterday
was not possible.
the past) because I’d hurt my leg. (past)
Couldn't have (done) for "Couldn't have" means something - We had a really good holiday. It
impossible past events was not possible in the past. couldn’t have been better.
Exercise 1: Put in can or could
Fill in the blanks with can or could where appropriate.
1. This is a wonderful place. I __________ stay here forever.
2. I’m so angry with him. I __________ kill him!
3. I __________ hear a strange noise. What is it?
4. It’s so nice here. I __________ sit here all day, but unfortunately, I have to go.
5. I __________ understand your point of view, but I don’t agree with you.
6. Peter is a keen musician. He plays the flute, and he __________ also play the
piano.
7. The company Amy works for isn’t doing well. She __________ lose her job.
8. Some people are unlucky. Life __________ be very unfair.
9. I’ve been really stupid. I __________ kick myself.
10. Be careful climbing that tree. You __________ fall.
Exercise 2: Complete the sentences
Choose the correct phrase from the box and fill in the blanks.
gone – could be – could come – could sleep – have moved – could have – could have
come – could have been
1. A: Are you tired?
B: Yes, very tired. I feel as if I __________ for a week.
2. A: I spent a very boring evening at home yesterday.
B: Why did you stay at home? You __________ out with us.
3. A: Shall I open this letter?
B: Yes. It __________ important.
4. A: How was your exam? Was it difficult?
B: It wasn’t so bad. It __________ worse.
5. A: I got very wet walking home in the rain.
B: Why did you walk? You __________ taken a taxi.
6. A: Where shall we meet tomorrow?
B: Well, I __________ to your office if you like.
7. A: Does Tom still live in the same place?
B: I’m not sure. He __________ .
8. A: Did you go to university?
B: No. I could have __________, but I didn’t want to.
Exercise 3: Complete the sentences with couldn’t or couldn’t have
Use the correct form of the verbs in the box.
afford – be – live – manage – stand – study – wear
1. I __________ in a big city. I’d hate it.
2. We had a really good holiday. It __________ better.
3. I __________ that hat. People would laugh at me.
4. You helped me a lot. I __________ without you.
5. The staff at the hotel were really good. They __________ more helpful.
6. There’s no way we could buy a car now. We __________ it.
7. Jack prepared for the exam as well as he could. He __________ harder.
8. I wouldn’t like to live near the motorway. I __________ the noise.
