A typical 3rd conditional uses this formula: If + subject + past perfect (had + past participle verb), subject + would have + past participle. The first half (If + subject + past perfect) is known as the 'conditional clause' or 'if clause'. The second half (subject + would have + past participle verb) is known as the 'main clause'. These can be placed in either order with no change in meaning. When the main clause comes first, we do not use a comma between them. If I had known you were coming, I would have baked a cake. I would have baked a cake if I'd known you were coming. Use The third conditional is used to wonder and imagine about past events that did not happen. If I'd been born in Spain, I would have learned Spanish, not English! What would you have done if you'd failed your test? #englishgrammar Comment your example