– Used to say that it is possible for sb/sth to do sth, or for sth to happen: Can you call back tomorrow? He couldn’t answer the question. The stadium can be emptied in four minutes.
– Used to say that sb knows how to do sth: She can speak Spanish. Can he cook?
– Used with the verbs ‘feel’, ‘hear’, ‘see’, ‘smell’, ‘taste’: She could feel a lump in her breast. I can hear music.
– Used to show that sb is allowed to do sth: You can take the car, if you want. We can’t wear jeans at work.
– Used to ask permission to do sth: Can I read your newspaper? Can I take you home?
– (Informal) used to ask sb to help you: Can you help me with this box? Can you feed the cat, please?
– Used in the negative for saying that you are sure sth is not true: That can’t be Mary—she’s in New York. He can’t have slept through all that noise.
– Used to express doubt or surprise: What can they be doing? Can he be serious? Where can she have put it?
– Used to say what sb/sth is often like: It can be quite cold here in winter.
– Used to make suggestions: We can eat in a restaurant, if you like. I can take the car if necessary.
– Used to say that sb must do sth, usually when you are angry: You can shut up or get out!
Can’t be doing with sth: (Informal) used to say that you do not like sth and are unwilling to accept it: I can’t be doing with people who complain all the time.
No can do: (Informal) used to say that you are not able or willing to do sth: Sorry, no can do. I just don’t have the time.
Can / may
Can and cannot (or can’t) are the most common words used for asking for, giving or refusing permission: Can I borrow your calculator? You can come with us if you want to. You can’t park your car there.
May (negative may not) is used as a polite and fairly formal way to ask for or give permission: May I borrow your newspaper? You may come if you wish. It is often used in official signs and rules: Visitors may use the swimming pool between 7 a.m. and 7 p.m. The form mayn’t is almost never used in modern English.
Can / could / be able to / manage
Can is used to say that somebody knows how to do something: Can you play the piano? It is also used with verbs of seeing, noticing, etc.: I can hear someone calling and with passive Infinitives: The DVD can be rented from your local store.
Can or be able to: are used to say that something is possible or that somebody has the opportunity to do something: Can you / are you able to come on Saturday?
You use: “be able to” to form the future and perfect tenses and the Infinitive: You’ll be able to get a taxi outside the station. I haven’t been able to get much work done today.
Could is used to talk about what someone was generally able to do in the past: Our daughter could walk when she was nine months old.
You use “was / were able to or manage” (but not could) when you are saying that something was possible on a particular occasion in the past: I was able to / managed to find some useful books in the library. In negative sentences, “could not” can also be used: We weren’t able to / didn’t manage to / couldn’t get there in time. Could is also used with this meaning with verbs of seeing, noticing, understanding, etc.: I could see there was something wrong.
Could have is used when you are saying that it was possible for somebody to do something in the past but they did not try: I could have won the game but decided to let her win.
1. Used as the past tense of ‘can’: She said that she couldn’t come. I couldn’t hear what they were saying. Sorry, I couldn’t get any more. Note at can1
2. Used to ask if you can do sth: Could I use your phone, please? Could we stop by next week?
3. Used to politely ask sb to do sth for you: Could you baby-sit for us on Friday?
4. Used to show that sth is or might be possible: I could do it now, if you like. Don’t worry—they could have just forgotten to call. You couldn’t have left it on the bus, could you? ‘Have some more cake.’ ‘Oh, I couldn’t, thank you (= I’m too full).’
5. Used to suggest sth: We could write a letter to the director
6. Used to show that you are annoyed that sb did not do sth: They could have let me know they were going to be late!
7. (Informal) used to emphasize how strongly you want to express your feelings: I’m so fed up I could scream! Note at modal
Could do with sth: (Informal) used to say that you need or would like to have sth: I could do with a drink! Her hair could have done with a wash.