Third conditional

The third conditional is used to imagine a different past. We imagine a change in a past situation and the different result of that change.

If I had understood the instructions properly, I would have passed the exam.
We wouldn't have got lost if my phone hadn't run out of battery.

In third conditional sentences, the structure is usually: If + past perfect >> would have + past participle.

Mixed conditionals

We can use mixed conditionals when we imagine a past change with a result in the present or a present change with a result in the past.

1. Past/Present 

Here's a sentence imagining how a change in a past situation would have a result in the present.

If I hadn't got the job in Tokyo, I wouldn't be with my current partner.

So the structure is: If + past perfect >> would + infinitive.

2. Present/Past

Here's a sentence imagining how a different situation in the present would mean that the past was different as well.

It's really important. If it wasn't, I wouldn't have called you on your holiday.

And the structure is: If + past simple >> would have + past participle.