Can and Could

Talent shows are a big thing now in our pop culture. If you want to participate in them, you should know how to talk about your abilities. Learn about it here!

"Can and Could" in English Grammar

'Can' and 'could' are both modal verbs that are mainly used to talk about abilities.

Can and Could Functions

We use them to:

Talking about Ability

One of the most common uses of the modals 'can' and 'could' is using them to talk about abilities.

Can

We can use can to talk about abilities we have because of our knowledge or talent in the present and the future.

I can drive.

She can sing really well.

Could

We can use could to talk about general abilities in the past. We use it to talk about what someone was able to do in the past.

My uncle could speak five languages.

By using this sentence, you understand that, maybe his uncle cannot still speak five languages, or maybe he is dead.

By the time he was seven, he could read and write.

Be able to or Can?

We cannot use can and could to talk about abilities in every situation. Sometimes we need to use other alternatives like be able to.
'Can' and 'be able to' generally have the same meaning. In this case, you can use either one of them. But it is more recommended to use 'can.' 'Be able to' is a little more formal than 'can.'

I can play the piano. = I am able to play the piano.

I could jump very high when I was younger. = I was able to jump very high when I was younger.

But, we cannot use can and could with every verb tense we want. For example if we want to talk about abilities in the perfect tenses, we should use be able to.

I have been able to dance since I was three years old.

Here, we cannot use 'can' or 'could' and still convey the same meaning.

As you might have noticed, we only use the base form of the verbs after modals like 'can' and 'could.' So, if we want to use gerunds, we should use be able to.

I like being able to watch my favorite TV shows on YouTube.

With verbs such as 'like' we need a gerund after them. So we cannot use 'can' or 'could' in this situations.

'Can' and 'could' can also be used with verbs of see, hear, understand, notice, etc. You cannot use 'be able to' with these verbs.

I can hear a noise.

Do not say "I am able to hear a noise."

I could understand every word he said.

Do not say "I was able to understand every word he said."

Be able to or Could?

Both 'could' and 'be able to' can be used to talk about abilities in the past. But they are not always interchangeable.
For example, if you want to talk about a specific ability or achievement you must use 'be able to' and using 'could' is wrong.

I was able to pass the driving test at the first try.

In this example, we are talking about a specific achievement in the past and we cannot use 'could' in this example.

I was able to reserve a table, although it was very busy.

In this example we are talking about an achievement so we cannot use 'could.'

You can use 'managed to' to talk about specific abilities in the past.

I managed to reserve a table, although it was very busy.

Using 'can' to show abilities

Specific or General Abilities in Affirmatives

You should only focus on the difference between specific or general abilities in the positive sentence. There's no need to distinguish between them in negative sentences.

I couldn't reserve a table.

No need to use 'to be able to' in a negative sentence.

I couldn't pass the driving test at the first try.

We cannot use two modal verbs in one sentence, i.e. we cannot use both 'can' or 'could' with other modals like 'should' or 'would.' In that case, we can use 'be able to' instead of can/could.

You should be able to choose your own religion. (Not You should can choose ...)

I would be able to give you an appointment for January 3rd. (Not I would can give you ...)

Could: Hypothetical or Real?

'Could' can have two different meanings:

  1. Could = was/were able to (abilities in the past)
  2. Could = would be able to (hypothetical ability in the future)

I could understand what he meant by that. = I was able to understand what he meant by that.

If you called me, I could help you. = If you called me, I would be able to help you.

Talking about Possibility

If you want to talk about something that is possible in the present or the future, you can use can and if you want to talk about possibilities in the past you can use could.

Can you come back tomorrow?

Here, the sentence means 'Is it possible for you to come back tomorrow.' So, can does not show an 'ability,' but it shows a 'possibility.'

The auditorium can be emptied in five minutes.

Could: Hypothetical or Real?

'Could' can have two different meaning:

  1. possibilities in the past
  2. hypothetical possibilities in the past

I couldn't have left it on the bus.

I could have done it, if you asked.

Could have is used when you are saying that it was possible for somebody to do something in the past but they did not try.

Requesting Something

We can use 'can' for requesting something. But keep in mind that, this use of 'can' is very informal.

Can I borrow your book?

Can you help me with my homework?

Making a Polite Request

'Could' is not necessarily used in the past tense. We can use 'could' in the present tense to make a polite request.

Could I have a glass of water, please?

Here, the request is being made politely at the present time.

Asking for or Giving Permission

We can use 'can' to ask permission to do something or to show that somebody is allowed to do something.

You can take the car, if you want.

In this sentence the person is giving permission.

Can we wear jeans at work?

we can use 'could' to ask permission to do something, politely.

Could I use your phone?

Can't or Cannot?

Sometimes the words 'can' and 'not' are written as one word: cannot. It's a formal word and it is used mostly in written English. In informal English, we use 'can't.'

He cannot believe what she's saying right now.

Review

Can is used a lot in daily English and even in formal writings. It has many functions. Now, look at the table.

To give or ask for permission Can I put my cloth on your bed?
to talk about abilities She can speak Spanish.
To request something informally Can you order us pizza.
To talk about possibilities Take your umbrella with yourself! It can be rainy outside.

Could is the past tense of 'can,' but it is not always talking about the past. Look at the chart below:

To talk about past abilities I could swim back then.
To make a polite request Could you please close the window?
To talk about possibilities in past Even now, I cannot believe us. It could be dangerous to be there.
To talk about hypothetical possibilities I could have been a Doctor by now if I studied more.

When it comes to expressing your ability, you can not always talk in present simple and past simple tenses, So, there must be an alternative for them in other tenses such as present perfect. In this case, you use be able to.

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