can, could and (be) able to
You can use can to talk about abilities in the present or the future:
 She can speak Spanish very well
 Can you come with us on Saturday?
You can use could to talk about general abilities in the past:
 I could run much faster when I was younger. = Any time I wanted.
 She could play the violin when she was a child. = She had this ability for a period of time.
Can and be able to have the same meaning, so you can usually use either verb without any difference in meaning:
 She can speak Spanish very well. = She’s able to speak Spanish very well.
 I could run much faster when I was younger. = I was able to run much faster when I was younger.
Can and could can’t be used in all verb tenses. If you want to use the present perfect (for example), there’s no way to use
can or could, so you need to use be able to:
 He’s been able to swim since he was two years old. –> There’s no way to use can or could in this sentence and keep
the same meaning.
 I like being able to choose my own working hours. –> After like we need a verb with -ing, so we need to use be able
to—there’s no way to use can or could.
There are many cases like this. Generally, if you have a choice, it’s better to use can/could, because it makes your
sentence simpler.
 We sometimes choose to use be able to, even when can/could are possible, because it sounds more formal.
3. How To Use Could and Be Able To to Talk about Ability in the Past
Look at an example sentence:
The traffic was really bad, but we could catch our train.
Does it sound right to you? If not, you’re right—the sentence is not correct.
Do you know why?
The answer is: this sentence is talking about a specific ability in the past.
In this sentence, we’re talking about a specific situation at a specific time. In this case, you can’t use could, we need to
use a different verb.
You could say:
 The traffic was really bad, but we were able to catch our train.
 The traffic was really bad, but we managed to catch our train.
To talk about an ability in a specific situation in the past, use was/were able to or managed to. For example:
 It was hard work, but we managed to finish everything on time. –> We finished something specific, at a specific
moment.
 Our car broke down on the way, but luckily I was able to fix it. –> I fixed it at a specific moment.
You can’t use could in these sentences.
There’s another complication here: this difference between general and specific situations only applies to positive
sentences.
In negative sentences, there’s no difference between could and be able to, whether the situation is general or specific:
 It was hard work, and we couldn’t finish everything on time.
 It was hard work, and we weren’t able to finish everything on time.
Even though this is a specific situation, we can use could because the sentence is negative.
So, to sum up, can/could and be able to generally have the same meaning, unless you are talking about a specific situation
in the past, and the sentence is positive.
 If you’re not sure about this, remember that you can use be able to in all of these sentences, and never be wrong.
We use can to say that something is possible or allowed, or that somebody has the ability to do something. We use can +
infinitive (can do / can see, etc.):
 We can see the lake from our hotel.
 ‘I don’t have a pen.’ ‘You can use mine.’
 Can you speak any foreign languages?
 I can come and see you tomorrow if you like.
 The word ‘dream’ can be a noun or a verb.
The negative is can’t (= cannot): I’m afraid I can’t come to the party on Friday.
You can say that somebody is able to do something, but can is more usual: We are able to see the lake from our hotel.
But can has only two forms: can (present) and could (past). So sometimes it is necessary to use (be) able to.
Compare:
 I can’t sleep.
 Tom can come tomorrow.
 Maria can speak French, Spanish and English.
 I haven’t been able to sleep recently.
 Tom might be able to come tomorrow.
 Applicants for the job must be able to speak two foreign languages.
Sometimes could is the past of can. We use could especially with:
See hear smell taste feel remember understand
 We had a lovely room in the hotel. We could see the lake.
 As soon as I walked into the room, I could smell gas.
 I was sitting at the back of the theatre and couldn’t hear very well.
We also use could to say that somebody had the ability to do something, or was allowed to do something:
 My grandfather could speak five languages.
 We were totally free. We could do what we wanted. (= we were allowed to do)
Could and was able to We use could for general ability and with see, hear, etc. :
 My grandfather could speak five languages.
 I could see them, but not very clearly.
But to say that somebody succeeded in doing something in a specific situation, we normally use was/were able to or
managed to (not could):
 The fire spread quickly, but everybody was able to escape. (not could escape)
 I didn’t know where Max was, but I managed to find him in the end. (not could find)
Compare:
• Jack was an excellent tennis player when he was younger. He could beat anybody. (= he was good enough to beat
anybody, he had the ability)
but
o Jack and Andy played a match yesterday. Andy played well, but Jack managed to beat him. (= he succeeded in
beating him this time)
The negative couldn’t (could not) is possible in all situations:
 My grandfather couldn’t swim.
 I looked for Max everywhere, but I couldn’t find him.
 Andy played well, but he couldn’t beat Jack.