THE THIRD CONDITIONAL
We turned left and we got lost.
If we hadn't turned left, we wouldn't have got lost. // We wouldn't have got lost if we hadn't turned left.
I didn't go by train because the ticket was so expensive.
If the ticket hadn't been so expensive, I would have gone by train. // I would have gone by train if the ticket hadn't been so expensive.
I didn't meet you at the airport because I didn't know when you were arriving.
If I had known when you were arriving, you would have met you at the airport. // I would have met you at the airport if I had known when you were arriving.