1. CAN and COULD

Can and could are modal verbs. They are used with other verbs to convey ideas such as possibility, permission, etc. We use can: to talk about possibility and ability; EXAMPLE: I can ride a horse. EXAMPLE: He can speak three languages. to make requests or give orders; EXAMPLE: Can you buy me a can of beer? EXAMPLE: Can you complete now what you are doing? to ask for or give permission. EXAMPLE: Can I come in now? Note: we may also use could, may and might for permission. when we decide we are able to do something for the present or future. EXAMPLE: We can have our dinner now. EXAMPLE: We can go swimming tomorrow. Could is one of the modal verbs. We use could: as the past tense of can. EXAMPLE: Jane said she could get the tickets for us. when we wish to be very polite. EXAMPLE: Could I go now, please? to show what was possible in the past. EXAMPLE: He could cycle when he was four years old. to ask someone to do something. EXAMPLE: Could you buy some cigarettes for me? to show the ability to do something. EXAMPLE: My grandmother could speak Spanish. to show that one is allowed to do something. EXAMPLE: We could choose to do the course we wanted. for an action now or in the future. EXAMPLE: It's a nice day. We could go for a walk. EXAMPLE: When I go to London next week, I could stay with my uncle for something that should have been done in the past. EXAMPLE: I was so tired. I could have slept the whole day. with present perfect tense for things which were possible to happen but didn't or an event which we are not sure about. EXAMPLE: You could have taken a different route to avoid the traffic jam. EXAMPLE: He could have broken the glass. / She couldn't have broken the glass. Points to note: We do not use can with infinitive verb. EXAMPLE: We can play football today. (NOT: We can to play football today.) We commonly use Can I to offer to do something EXAMPLE: Can I help you to do it? Sometimes it is necessary to use (be) able to in place of can. EXAMPLE: I can't contact him. / I haven't been able to contact him for two days. (It is not possible to use can with present perfect tense). Where the subject is singular, we do not add –s to the verb following can or could EXAMPLE: He can swim. (NOT: He can swims.) EXAMPLE: We could smell burning. (NOT: We could smells burning) Could is less sure than can, so we use could when we do not really mean what we say. EXAMPLE: I am so hungry. I could eat the whole chicken. (NOT: I can eat the whole chicken).