Modal verbs - Can
As a simple expression of ability or permission to do something, can is not very difficult. For example, Can you swim? or I can use his car when he's on holiday . Unlike the other modals, can also has a past simple form could, as in the sentences I could walk before I was one, or I couldn't find my keys this morning.
However, could has other functions and is not always so easy to use correctly. The following questions will show the complexity of this modal for English learners.
Quiz
1. This quiz tests your ability to choose the right form of the verb can in the different tenses to express either ability or permission.
- Some time in the future doctors will ...... cure cancer.
- The door was locked but I ...... get in through the window.
- She ...... to enter the concert even though she didn't have a ticket.
- I would love ...... ride a horse.
- I don't think I ...... go to the party. My parents are very strict.
- Finally, after trying all day I ...... find exactly the dress I was looking for.
- The question was very easy. It ...... be answered by everyone.
- Some time in the future doctors will be able to cure cancer. ( could is NOT possible here)
- The door was locked but I was able to get in through the window. ( could is just possible here too)
- She was allowed to enter the concert even though she didn't have a ticket. ( could is NOT possible here)
- I would love to be able to ride a horse.
- I don't think I will be allowed to go to the party. My parents are very strict. ( can is possible here, but could is not)
- Finally, after trying all day I was able to find exactly the dress I was looking for. ( could is NOT possible here)
- The question was very easy. It could be answered by everyone. ( was able to be is NOT possible here)
2. What does could mean in each of the following sentences.
- Could you tell me the answer?
- He could tell you the answer.
- He could have told you the answer.
- This could be the answer!
- Could you tell me the answer? means Will you please tell me the answer? Could is very often used to make a polite request.
- He could tell you the answer . This does not mean that he did in fact tell you the answer. It means he knows enough to be able to answer your question if you ask him.
- He could have told you the answer . This means that he had the ability to answer your question, but he didn't (possibly because you didn't ask him!)
- This could be the answer means that there is a possibility this is the answer.
3. Why is could needed in the first sentences below and was able to in the second?
- I could read by the age of four.
- I was able to read the report on the way to the airport.
- When I was younger I could run the marathon in under 3 hours.
- I was able to run the Berlin marathon in less than 3 hours.
In the first sentence in each case above, could is used to talk about a past ability. Whereas in the second sentence in each case was able to is needed to talk about a single past action.
4. Which, if any, of the following sentences is not possible? Explain the meanings of each sentence. (Some have more than one meaning.)
- He could win the race.
- He could have won the race.
- He couldn't win the race.
- He couldn't have won the race.
All the sentences are possible, although He couldn't win the race , standing alone, seems unlikely. In the answer to quiz 3 above I explained that could is not usually used when referring to a past action rather than a past ability.
In fact, it can be used in negative sentences or questions. E.g. I'd lost my key, so I couldn't get in. The sentence in question is possible in the following context: He couldn't win the race, because he had forgotten to bring the right shoes (although, even here it does not sound quite right; more likely is: He didn't win... )
For the reason explained in answer 3, He could win the race does not mean that the race is over and he won it. It means that the race is in the future and he has a chance of winning it. If you want to negate the possibility that he will win, you do not say He couldn't win the race , you say something like He has no chance of winning.
He could have won the race . This means the race is over and he did not win. He had a chance of winning but through bad luck or by not training hard enough etc., he did not win. It could also mean that the race is over and it is possible that he won, but I didn't see the finish so I am not sure.
He couldn't have won the race also has two possible meanings: Firstly, it implies that the race is over but I do not know the result. However, I am deducing that he did not win or expressing my doubt that he did. E.g. He couldn't have won the race, because I saw him fall and twist his ankle at the 3-mile mark.
The second meaning is that the race is over and (I know) he didn't win, but I am saying that he had had no chance of winning. E.g. He couldn't have won the race, even if he had had an engine on his back .
But again, this use of could seems a little strained. More likely is: He wouldn't have... or He had no chance of... .
5. Finally, a quick question. Is there anything wrong with this short dialogue?
- Could I borrow your pen, please? - Yes, you could!
The answer Yes, you could is possible only if the speaker is trying to be funny. The usual response to the polite question Could I...? is Yes, you can!
The answer Yes, you could!, with stress on the word could, implies the irritating continuation Yes, you could but I'm not going to let you or Yes, you could if you asked very nicely! etc.