The use of can is as follows.
a. General possibilities
1 You can ski on the hills. There is enough snow.
2 We cannot bath here on account of sharks (it is unsafe)
3 Can you get to the top of that mountain in one day? (if is impossible).
You might have noticed that possibility/impossibility shown in the above sentences is not meant only for one person but for general public (for all).
The factors making possible or impossible are external.
1 She can speak English.
2 Fish cannot swim out of water.
3 He can help you.
The ability or otherwise depends upon the individual. The individual is capable or not capable of doing something.
Can I borrow your car? Of Course, you can/cannot.
c. For Orders
1 This is awful word. You cannot do it again.
2 You cannot go there again.
3 You cannot leave office early.
1 Can I help you?
2 I can give you this pen if you hurry?
You can catch the 7:30 train if you hurry.
In several cases the use of ‘May’ is just the same as of ‘Can’.
1 May I borrow this book.
2 Of course you may.
3 Only the members may play in the club.
1 You may stay with me.
2 May I help you?
1 You may be right here but I don’t agree with you.
2 You may be old but does not excuse you from this duty.
3 He has not phoned. He may not know the number.
d. May and Can Together
1 We can have a picnic but we may not (we have the opportunity but we won’t take advantage of it).
2 We may have a picnic but we can’t. (it expresses likelihood but at the same time we don’t have the permission)
a. It shows permission in past
I could use my father’s car whenever I liked.
b. Expresses ability in past
1 She could speak English when she was six.
2 They could not find the way home that night.
It may be noted that “Could” is the past tense of “Can” and we have seen in the above sentences that it has been used for past time, but now let us see how we can use it for other times.
1 Could I borrow your car next week (it shows permission, asking for permission for future).
2 Could You hold the door open for me (it is request for present time).
3 You could type this for me now/tomorrow (it is an order for present time or future).
4 Come early so we could have a picnic (it is a suggestion for present/future).
5 There could be life on some of the planets (possibility for present/future).
It is used to show possibilities.
1 Don’t tell him anything, he might tell others.
2 He might know Shahid’s address.
It may be noted here that in these sentences we can mean both present and future times. We can have some more examples.
1 He might be waiting at the railway station.
2 He might be doing his homework when we visit him at 9:00 tonight.
a. Speculation about past
He might have left for Karachi.
Here we guess or imagine about his leaving for Karachi but we are to sure whether he left or not.
It can be used in conditional sentences. (We will discuss about the conditional sentences later on in this unit). It shows a possible result.
1 If you poured hot water into it, it might crack (for future).
2 If you had left it there someone might have stolen it (past).
a. It is used to express a repeated action in the past.
When I was a child, my father would read me a story every night before bed.
It means my father used to read stories.
b. Used in Soft Statements.
I would like a cup of tea.
Note: “I want” is a strong statement.
c. Used for expressing preference
I would rather go to a movie tonight then to study grammer.
d. Expresses Polite Requests
1 Would you mind opening the window?
2 Perhaps you would like to help me with this language.
3 Would you help me please?
a. It is used to express advisability when we advise someone.
1 You should lose some weight.
2 You should not leave your keys in the car.
b. It is used to express an idea.
I should wait for him before I start this work.
c. For obligation
You should listen to your parents.
Shahid should be in the department soon. (We assume here that he will be in the department soon).
a. It expresses necessity
1 Ali’s driver must have license.
2 I must be at home at night. I am expecting an important telephone call at night.
3 You must not tell anyone about this.
b. It expresses probability
Why is not Amir in the class? He must be sick.
It must be noted that the speaker is not sure about the sickness of Amir, but he has some reason for making him believe that Amir is sick and that is, let us suppose, he saw him last night, he was not feeling well.
a. It is used to express advisability.
1 You ought to lose some weight.
2 You ought to study harder.
b. Can be used for expressing expectation.
1 The bus ought to be here soon.
2 The bus ought to have been here 10 minutes ago (but it has not come whereas it was expected to be here 10 minutes before).