Definition of can modal verb from the Oxford Advanced Learner's Dictionary

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can

1modal verb
kən
 
; kən
 
kæn
 
; strong form kæn
 
 
see also can2 negative cannot
ˈkænɒt
 
; ˈkænɑːt
 
short form can't
kɑːnt
 
; kænt
 
past tense could
kəd
 
; kəd
 
kʊd
 
; kʊd
 
negative could not short form couldn't
ˈkʊdnt
 
; ˈkʊdnt
 
1 used to say that it is possible for somebody/something to do something, or for something to happenI can run fast.Can you call back tomorrow?He couldn't answer the question.The stadium can be emptied in four minutes.I can't promise anything, but I'll do what I can.Please let us know if you cannot attend the meeting.2 used to say that somebody knows how to do somethingShe can speak Spanish.Can he cook?I could drive a car before I left school.3 used with the verbs ‘feel’, ‘hear’, ‘see’, ‘smell’, ‘taste’She could feel a lump in her breast.I can hear music.4 used to show that somebody is allowed to do somethingYou can take the car, if you want.We can't wear jeans at work.5 (informal) used to ask permission to do somethingCan I read your newspaper?Can I take you home?6 (informal) used to ask somebody to help youCan you help me with this box?Can you feed the cat, please?7 used in the negative for saying that you are sure something is not trueThat can't be Mary—she's in New York.He can't have slept through all that noise.8 used to express doubt or surpriseWhat can they be doing?Can he be serious?Where can she have put it?9 used to say what somebody/something is often likeHe can be very tactless sometimes.It can be quite cold here in winter.10 used to make suggestionsWe can eat in a restaurant, if you like.I can take the car if necessary.11 (informal) used to say that somebody must do something, usually when you are angryYou can shut up or get out!
Idioms

can't be doing with somebody/something/somebody doing something

(informal) used to say that you do not like something and are unwilling to accept itI can't be doing with people who complain all the time.I can't be doing with you moaning all the time.

no can do

(informal) used to say that you are not able or willing to do somethingSorry, no can do. I just don't have the time.
Usage noteUsage note: can / mayCan 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. Students may not use the college car park. The form mayn’t is hardly ever used in modern English.Usage noteUsage note: can / could / be able to / manageCan 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. She’d love to be able to play the piano.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. I could 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.Usage noteUsage note: modal verbsThe modal verbs are can, could, may, might, must, ought to, shall, should, will and would. Dare, need, have to and used to also share some of the features of modal verbs.Modal verbs have only one form. They have no -ing or -ed forms and do not add -s to the 3rd person singular form:He can speak three languages. She will try and visit tomorrow.Modal verbs are followed by the infinitive of another verb without to. The exceptions are ought to, have to and used to:You must find a job. You ought to stop smoking. I used to smoke but I gave up two years ago.Questions are formed without do/does in the present, or did in the past:Can I invite Mary? Should I have invited Mary?Negative sentences are formed with not or the short form -n’t and do not use do/does or did.You will find more help with how to use modal verbs at the dictionary entries for each verb.