Frequency: The word is one of the 700 most common words in English.
Note: 'Could' is a modal verb. It is used with the base form of a verb. 'Could' is sometimes considered to be the past form of 'can', but in this dictionary the two words are dealt with separately.
1.
You use ~ to indicate that someone had the ability to do something. You use ~ not or ~n’t to say that someone was unable to do something.
For my return journey, I felt I ~ afford the extra and travel first class...
I ~ see that something was terribly wrong...
When I left school at 16, I ~n’t read or write...
There was no way she ~ have coped with a baby around.
MODAL
2.
You use ~ to indicate that something sometimes happened.
Though he had a temper and ~ be nasty, it never lasted...
He ~ be very pleasant when he wanted to.
MODAL
3.
You use ~ have to indicate that something was a possibility in the past, although it did not actually happen.
He ~ have made a fortune as a lawyer...
He did not regret saying what he did but felt that he ~ have expressed it differently.
MODAL
4.
You use ~ to indicate that something is possibly true, or that it may possibly happen.
Doctors told him the disease ~ have been caused by years of working in smokey clubs...
An improvement in living standards ~ be years away...
= might
MODAL
5.
You use ~ not or ~n’t to indicate that it is not possible that something is true.
Anne ~n’t be expected to understand the situation...
He ~n’t have been more than fourteen years old.
MODAL
6.
You use ~ to talk about a possibility, ability, or opportunity that depends on other conditions.
Their hope was that a new and better East Germany ~ be born...
I knew that if I spoke to Myra, I ~ get her to call my father.
MODAL
7.
You use ~ when you are saying that one thing or situation resembles another.
The charming characters she draws look like they ~ have walked out of the 1920s.
MODAL
8.
You use ~, or ~n’t in questions, when you are making offers and suggestions.
I ~ call the local doctor...
You ~ look for a career abroad where environmental jobs are better paid and more secure...
It would be a good idea if you ~ do this exercise twice or three times on separate days.
MODAL
9.
You use ~ in questions when you are making a polite request or asking for permission to do something. Speakers sometimes use ~n’t instead of ‘~’ to show that they realize that their request may be refused.
Could I stay tonight?...
Could I speak to you in private a moment, John?...
He asked if he ~ have a cup of coffee...
Couldn’t I watch you do it?
MODAL politeness
10.
People sometimes use structures with if I ~ or ~ I as polite ways of interrupting someone or of introducing what they are going to say next. (FORMAL, SPOKEN)
Well, if I ~ just interject...
Could I ask you if there have been any further problems?...
First of all, ~ I begin with an apology for a mistake I made last week?
= may
MODAL politeness
11.
You use ~ to say emphatically that someone ought to do the thing mentioned, especially when you are annoyed because they have not done it. You use why ~n’t in questions to express your surprise or annoyance that someone has not done something.
We’ve come to see you, so you ~ at least stand and greet us properly...
Idiot! You ~ have told me!...
He ~ have written...
Why ~n’t she have said something?...
MODAL emphasis
12.
You use ~ when you are expressing strong feelings about something by saying that you feel as if you want to do the thing mentioned, although you do not do it.
‘Welcome back’ was all they said. I ~ have kissed them!...
She ~ have screamed with tension.
MODAL emphasis
13.
You use ~ after ‘if’ when talking about something that you do not have the ability or opportunity to do, but which you are imagining in order to consider what the likely consequences might be.
If I ~ afford it I’d have four television sets...
If only I ~ get some sleep, I would be able to cope.
MODAL
14.
You use ~ not or ~n’t with comparatives to emphasize that someone or something has as much as is possible of a particular quality. For example, if you say ‘I ~n’t be happier’, you mean that you are extremely happy.
The rest of the players are a great bunch of lads and I ~n’t be happier...
The news ~n’t have come at a better time.
MODAL emphasis
15.
In speech, you use how ~ in questions to emphasize that you feel strongly about something bad that has happened.
How ~ you allow him to do something like that?...
How ~ she do this to me?...
MODAL emphasis
16.
~ do with: see do