The third conditional

We form the third conditional by using the past perfect after 'if' and then 'would have' and the past participle in the main clause:

if + past perfect, ...would + have + past participle

It talks about the past. It's used to describe a situation that didn't happen, and to imagine the result of this situation.

• If she had studied, she would have passed the exam. (but, really we know she didn't study and so she didn't pass)
• If I hadn't eaten so much, I wouldn't have felt sick. (but I did eat a lot, and so I did feel sick)
• If we had taken a taxi, we wouldn't have missed.
• She wouldn't have been tired if she had gone to bed earlier. (but she did not go to bed earlier and she was tired)
• She would have become a teacher if she had gone to university. (but she did not go to university and she did not become a teacher)