Modal Verbs Can and Could
'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.
We can use can to talk about abilities we have because of our knowledge or talent in the present and the future.
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.
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
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.'
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.
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.
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.
Do not say "I am able to hear a noise."
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.
In this example, we are talking about a specific achievement in the past and we cannot use 'could' in this example.
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.
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.
No need to use 'to be able to' in a negative sentence.
should can choose ...)
would can give you ...)
Could: Hypothetical or Real?
'Could' can have two different meanings:
- Could = was/were able to (abilities in the past)
- Could = would be able to (hypothetical ability in the future)
If you called me, I
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.
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.'
Could: Hypothetical or Real?
'Could' can have two different meaning:
- possibilities in the past
- hypothetical possibilities in the past
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.
We can use 'can' for requesting something. But keep in mind that, this use of 'can' is very informal.
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.
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.
In this sentence the person is giving permission.
we can use 'could' to ask permission to do something, politely.
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.'
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||
|to talk about abilities||
|To request something informally||
|To talk about possibilities||
Take your umbrella with yourself! It
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||
|To make a polite request||
|To talk about possibilities in past||
Even now, I cannot believe us. It
|To talk about hypothetical possibilities||
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.