Hi everybody, my name is Alicia.

In this lesson I'm going to talk about could have, should have, and would have what they mean,

how to use them in the negative, and the differences between them.

So, let's get started.

First, I want to begin with could have.

Let's look at the positive and the negative meanings of could have.

First, positive.

We use could have, positive, for something that was possible in the past.

So to give kind of an image of this, if our conversation is happening now, when we use could have, we're talking about something that had

possibility in the past, something we were able to do, for example.

An example sentence, ah, if I had known you were throwing a surprise party, I could have helped.

I could have helped.

So here could have shows us that this action, helping, was possible in the past.

In this case, the speaker did not know some information,

and as a result this action did not happen but

it was possible at a point in the past the speaker could have helped helping was a

possibility in the past so we use could have to express that possibility the

negative form however expresses the opposite. So in the negative

could not have, expresses something that was impossible, impossible, so not possible in the past.

So here, if we want to give an image, it's something that was not possible,

something we were not able to do. Let's look at an example of this. No, that couldn't

have been Sarah in the cafe just now. She's at the office. So here I'm using couldn't have, could not have,

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