TESOL/Use of can and could

The use of can & could is related to something possible or allowed. This also relates to showing ability of a person to do some activity.

Ex.
 * 1) I can see the river from my terrace.
 * 2) I have lost my pen. Do not worry ‘you can use my pen’.
 * 3) Can you speak English fluently?
 * 4) She can visit tomorrow so be prepared for surprises.
 * 5) The word ‘game’ can be used differently as per the need and comfort.

Cannot

 * 1) I cannot drink milk.
 * 2) He cannot play cricket.

Forms of can
There are two forms of can:- can (present) and could(past). Use of Could:-‘Could as past of can’ Mostly could is in use with the following words:- See, hear, smell, taste, feel, remember, understand
 * 1) The moment I entered in the room, I could smell gas.
 * 2) I had a lovely room in the building. I could see the river.
 * 3) She was sitting in the bus and I could not hear her voice on phone.
 * 4) I was eating lunch in the hotel. I could not match the taste with the breakfast.
 * 5) He could remember a dictionary.
 * 6) She could not understand the gravity of the situation.

Express abilities / permission:-
 * 1) My grandmother could speak six languages.
 * 2) We were totally free. We could do what we wanted.

Compare :-
 * 1) Ram was an excellent player when he was young .He could beat anybody.
 * 2) The situation was very serious but she could not understand.

The negative ‘could not’ is possible in all situations:-
 * 1) My father could not swim.
 * 2) The British government tried a lot, but they could not find Subhash Chandar Boss.
 * 3) Australia played well, but they could not win the match.

Use of could & could have
A. We use could to talk about possible actions now or in the future especially to make suggestions:-

For example:-

1. What shall we do this evening? Ans. We could go to the market.

2. When you go to Chandigarh next time, you could stay with Raj. Ans. Yes, I suppose I could.

Choice of use ‘can’ here is possible (we can go to the market etc.) With could the suggestion is less sure.

B. We also use could for actions which are not realistic.

Ex.:-
 * 1) I am tired, I could sleep for a week.{not I can}

See can / could comparison:-
 * 1) I can stay with Pooja when I go to Chandigrh.{realistic}
 * 2) May  be I could stay with Pooja when I go to Chandigarh.{possible but not sure}
 * 3) Uttar Kashi is a wonderful place. I could stay here for ever.(unrealistic)

C. Use of could have:-
 * 1) I am so tired, I could sleep for a week.(now)
 * 2) I was so tired, I could have slept for a week.(past)
 * 3) The condition is bad, but it could be worse.(now)
 * 4) The condition was bad, but it could have been worse.(past)

D. Something could have happened =was possible but did not happened
 * 1) Why did you stay at a hotel when you were in Chandigarh.You could have stayed with Pooja.
 * 2) I did not know that you wanted to go to the movie.I could have got you a ticket.
 * 3) Khushi was lucky. She could have hurt herself when she fell, but she is ok.

We use could not to say that something would not be possible now:-
 * 1) I could not live in a big city. I would had it.
 * 2) All is well now.Things could not be better.

For the past we use could not have :-


 * 1) We had a really good trip. It could not have been better.
 * 2) The trip was cancelled last week. Ravi could not have gone anyway because he was ill.