could

could [ weak kəd, strong kud ] modal verb ***

Could is usually followed by an infinitive without to :

I'm glad you could come. Sometimes it is used without a following infinitive:

I came as quickly as I could.

Could does not change its form, so the third person singular form does not end in -s :

She could play the violin when she was six.

Questions and negatives are formed without do :

Could he help you?

I could not breathe.

The negative form could not is often shortened in conversation or informal writing to couldn't:

I couldn't find her phone number.

Could is often used in tag questions:

They couldn't see us, could they?

Could has no tenses, no participles, and no infinitive form.

There is no past tense, but could have followed by a past participle is used for referring to something in the past that was not real, or something that may possibly have been real:

I could have been killed.

What was that noise? Could it have been the wind?

Could is used as the past tense of can when it means that someone had the ability to do something, or that something was possible:

The Roman army could march 30 miles in a day.

1. ) past tense of can used as the past tense of can :

Renee could already read when she was four.

In the distance I could see a cloud of smoke.

2. ) in requests SPOKEN used in polite requests, or when offering or suggesting something:

Could I have a glass of water?

Could you mail this letter for me?

=> CAN1

3. ) saying what is possible

a ) used for saying that something is possible or that it may happen:

We could still win the game isn't over yet.

In a situation like this, anything could happen.

could easily: You could easily get lost in the dark.

b ) SPOKEN used for suggesting to someone a possible course of action, especially when they are in a difficult situation:

You could come and stay with us.

could always: You could always sell the cabin if you need some extra cash.

4. ) expressing annoyance SPOKEN used for showing that you are annoyed at the way someone has behaved:

How could you be so cruel!

They could at least have said they were sorry.

5. ) for emphasis SPOKEN used for emphasizing how angry, happy, bored, etc. you are:

It's all Helen's fault. I could strangle her!

When I heard the news, I was so happy I could have cried.

could have (done something) SPOKEN

1. ) used for saying that something was possible in the past, even though it did not happen:

You could have been killed.

I could have told you, but I didn't think you would listen.

She could have married Gerald if she'd wanted to.

2. ) used for saying that perhaps something was true, although you do not really know:

The explosion could have been caused by a gas leak.

It could have been Dan, but I'm not sure.

couldn't be better/worse/nicer etc. MAINLY SPOKEN

used for emphasizing that someone or something is extremely good/bad/nice etc.:

The two brothers couldn't be more different (=they are very different).

I was so nervous, but she couldn't have been nicer to me.

I couldn't MAINLY BRITISH SPOKEN

used for politely saying no when someone offers you something:

More ice cream? No, thanks. I couldn't.

I couldn't ask/wish for... SPOKEN

used for saying that something is so good, you cannot imagine anything better:

I couldn't wish for a better husband.

We got fantastic support we couldn't have asked for more.

=> CARE1