The 3rd conditional: What is it? How to use it! - English In A Minute - YouTube

Welcome to BBC Learning English.

I'm Sam and today we're talking about

the third conditional.

The third conditional is a little strange

because we're talking about something that

didn't happen in the past.

Why would we do that?

Well, because sometimes we want to imagine

a different outcome.

A friend of mine came to visit me yesterday.

It was a surprise, so when I opened my front door, I said:

"If I'd known you were coming,

I would have baked a cake!"

Did I know she was coming? No.

Did I bake a cake? No.

So I'm imagining a different result.

Because we're talking about an imaginary past,

we use:

If + the subject + the past perfect,

the subject + would have + past participle

And you can also swap those round:

What would you have done

if you'd known your friend was coming?