A. We use could in a number of ways. Sometimes could is the past of can.
Listen. I can hear something. (now) I listened. I could hear something. (past) But could is not only used in this way. We also use could in the future (especially to make a suggestion).
For example: A: What shall we do this evening? B: We could go to the cinema. It's a nice day. We could go for a walk. When you go to New York next month, you could stay with Barbara. A: If you need money, why don't you ask Karen? B: Yes, I suppose I could.
Can is also possible in these sentences ('We can go for a walk,' etc.). Could is less sure than can. You must use could (not 'can') when you don't really mean what you say. For example: I'm so angry with him. I could kill him! (not 'I can kill him')
B. We also use could to say that something is possible now or in the future: The phone is ringing. It could be Tim. I don't know when they'll be here. They could arrive at any time.
Can is not possible in these examples (not 'It can be Tim')
In these sentences could is similar to might : The phone is ringing. It might be Tim.
C. Compare could (do) and could have (done): I'm so tired. I could sleep for a week. (now) I was so tired. I could have slept for a week. (past)
Most often, we use could have (done) for things which were possible but did not happen: Why did you stay at a hotel when you went to New York? You could have stayed with Barbara. (= you had opportunity to stay with her but you didn't) Jack fell off a ladder yesterday but he's all right. He's lucky! He could have hurt himself badly. (but he didn't hurt himself) The situation was bad but it could have been worse.
D. Sometimes could means 'would be able to...': We could go away if we had enough money.(= we would be able to go away) I don't know how you work so hard. I couldn't do it.
Could have (done) = would have been able to (do): Why didn't Liz apply for the job? She could have got it. We could have gone away if we'd had enough money. The trip was cancelled last week. Paul couldn't have gone anyway because he was ill. (= he wouldn't have been able to go) You did very well to pass the exam. I'm sure I couldn't have passed it. (= I wouldn't have been able to pass it if I had taken it)
Exercise 1: Answer the questions with a suggestion. Use could. 1. What shall we have for dinner tonight?(fish) We _______________ 2. What shall I give Ann for her birthday?(a book) You ______________ 3. When shall I phone Angela?(now) ____________________ 4. When shall we go and see Tom?(on Friday) ____________________ 5. Where shall we hang this picture?(in the kitchen) __________________
Exercise 2:Put in can or could. Sometimes, either word is possible. 1. I'm really hungry. I _____________ eat a horse! 2. If you're very hungry, we ____________ have dinner now. 3. It's so nice here. I ________ stay here all day but unfortunately I have to go. 4. 'I can't find my bag. Have you seen it?' 'No, but it __________ be in the car.' 5. Peter is a keen musician. He plays the flute and he _________ also play the piano.
Chris: Hello, Julia! Your mom told me you just had you vacation last week in Tuscany. How was it?
Julia: It's great. The first time I visited Tuscany, it captivated me so much I could have stayed there and never came back. I was especially drawn to the countryside where the sunshine bounces off the wide sunflower fields and the quaint little cottages that were scattered thoughout. The glade was so golden in summer you could have thought it was made of gold! The people were nice and friendly. I could never have had a greater time staying with them.
Chris: Wow, that's fantastic! Sounds like you went to a beautiful vacation.
Julia: Yes, I did. The scenery was fabulous, I could have stayed outside for the whole day.
Chris: How I wish I could have chosen Tuscany to spend my vacation last summer.
Julia: Don't worry, Chris... we still have Christmas vacation. We could go there together and enjoy camping.
1. What could you do to help your country? 2. What could you have done to improve yourself? 3. What could you do to contribute to the success of the company? 4. What could you do to fight pollution? 5. What could you have done when you went on vacation?
