The third conditional
The Third Conditional is formed by 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 the show. (but we didn't take a taxi and so we missed the show)
- She wouldn't have been tired if she had gone to bed earlier. (but she did not go to bed earlier and so she was tired)
- She would have become a teacher if she had gone to university. (but she did not go to university and so she did not become a teacher)