Can, could and (be) able to

Learn and practise the use of can, could and (be) able to.

A 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.

B 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.
• I haven’t been able to sleep recently.

• Tom can come tomorrow.
• Tom might be able to come tomorrow.

• Maria can speak French, Spanish and English.
• Applicants for the job must be able to speak two foreign languages.

C 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)

D 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

• 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.