Ability and inability: can, could, be able to

Can is used to talk about the general ability or inability to do something in the present and in the future.

I can dance very well. /He can't speak French./Can you play the guitar?

Could is used to say that someone had the general ability or inability to do something in the past.

I could swim when I was 3 years old. /His grandfather couldn't read./ Could she read music when she was 6?

BE ABLE TO instead of CAN/COULD

We can use am/is/are able to instead of can to talk about the general ability or inability in the present, but can is more usual in this case.

Are you able to dance very well?

We also use was/were able to instead of could to say that someone

1) had the general ability or inability to do something in the past

I was able to/could swim when I was 3 years old.

2) managed to do something in a particular situation in the past.

We were able to find time to discuss it.

NOTE:

1. With the verbs of perception and understanding we usually use could to say that we managed to do something in a particular situation:

see, hear, smell, taste, feel, understand, remember, etc.

There was such a noise that we couldn't hear anything.

I could see a few stars in the sky.

2. We use could not (couldn't) instead of wasn't /weren't able to to say that we didn't manage to do something in the past.

He tried very hard but he couldn't swim back to the boat.

We use will be able to instead of can to talk about the general ability or inability to do something in the future.

Nobody else will be able to do that.

We use be able to for the Present/Past Perfect.

Since his accident he hasn't been able to leave the house.

He said that he had lost his passport and hadn't been able to leave the country.

Exercise 2. Complete the sentences with can, can't, could or couldn't.

Example: It was a huge hall and we were at the back, so we couldn't hear very well.

Look! I can stand on my head.

1. I count to twenty in Italian.

2. Put up your hand if you hear me.

3. There was a woman with a big hat in front of me. I see a thing.

4. My mother understand sign language.

5. When Mason was 7, he swim like a fish.

6. We all read and write.

7. When Lily was younger she run very fast.

8. I find my front door key last night.

Exercise 3. Complete the sentences. Use the correct form of be able to.

Example: Our baby will be able to walk in a few weeks.

I was able to contact him at the office yesterday.

She hasn't been able to dance since she had a car crash.

1. It was rather cheap — I buy it.

2. It took a long time, but in the end Frank buy his own car.

3. I come tomorrow. I'm afraid, I'm too busy.

4. Our teacher says we speak English fairly well in a few months.

5. He work since his illness.

6. Unfortunately we get the tickets for the match yesterday.

Exercise 4. Complete the sentences. Use can(not), could(n't) or be able to. Where two answers are possible, write them both.

Example: When I was young I could/was able to climb any tree in the forest.

I'm afraid I won't be able to attend the conference tomorrow.

She has been able to write poems since she was 10.

1. I generally leave work at seven, but I leave earlier on Fridays.

2. He read the message but he understand it.

3. Clare sing really well when she was a young girl.

4. Look! You see the mountains from this window.

5. The box was so heavy that he lift it.

6. I play the piano since I was 5.

7. I'm really sorry, but I come to the party on __ Sunday.

8. They were talking quite loudly. I hear everything they said.