Third conditional 是什么，什么时候使用？
Third conditional，也叫第三类条件句，把两个与事实相反的过去事件联系起来。先设想一个没有发生的条件，再说明如果该条件不同，可能出现什么结果。
我错过了火车。
如果我早点出发……
……我就不会错过它。
英语 third conditional 的结构
该结构在 if 从句中使用 past perfect，在结果句中使用 would have + 过去分词。两个从句可以交换顺序，含义不变。
| 形式 | 结构 | 例句 |
|---|---|---|
| 肯定句 | If + subject + had + past participle, subject + would have + past participle | If she had studied, she would have passed. |
| 否定句 | If + subject + had not + past participle, subject + would not have + past participle | If we had not rushed, we would not have made that mistake. |
| 疑问句 | Would + subject + have + past participle + if + subject + had + past participle? | Would you have gone if you had known? |
| 使用 could / might | If + past perfect, subject + could/might have + past participle | If he had trained, he might have won. |
if 从句在前时使用逗号；如果它位于结果句之后，通常不需要逗号。
Third conditional 的用法：遗憾、批评和过去的另一种可能
表达遗憾
回顾过去并说明什么本可以改变。
错失机会
设想没有抓住的机会本可能带来的结果。
评价过去
把过去的原因与后果联系起来。
表达庆幸
说明某件事没有发生为什么反而是好事。
带解释的 third conditional 例句
把每个句子看成两条时间线：一条是真实发生的过去，另一条是只存在于想象中的替代版本。
决定
学习与工作
旅行与相遇
Second conditional 与 third conditional 的区别
Second conditional设想不太可能的现在或未来；third conditional重构已经无法改变的过去。
If I had more time, I would travel. — 我现在没有时间；这里设想的是另一种现在。
If I had had more time, I would have travelled. — 我当时没有时间，所以旅行没有发生。
Third conditional 的常见错误
如何不逐字翻译地构造 third conditional
先想故事，再想公式。找出过去的事实，在脑中把它反转，然后补上另一种结果。
说清楚真实发生了什么。
用 had + 过去分词构造相反条件。
用 would/could/might have + 过去分词构造结果。
确认两个动作都属于已经结束的过去。
Third conditional 练习及答案
先完成句子，再展开答案。然后用英语说出真实发生的情况。
- If I ___ (know) about the delay, I ___ (leave) later.
- They ___ (not miss) the train if they ___ (set) an alarm.
- What ___ you ___ (do) if you ___ (receive) the offer?
查看答案
had known / would have left; would not have missed / had set; would / have done / had received.
选择正确的句子：
Third conditional 常见问题
Third conditional 的公式是什么？
If + 主语 + had + 过去分词，主语 + would have + 过去分词。Could have 和 might have 可表达能力或可能性。
Had had 是什么意思？
第一个 had 是 past perfect 的助动词，第二个是 have 的过去分词。If I had had time 表示“如果我当时有时间”。
两个从句可以交换顺序吗？
可以。If I had known, I would have called 与 I would have called if I had known 含义相同。
Would have 和 could have 有什么区别？
Would have 表示预期结果；could have 突出能力或选择；might have 表示较不确定的可能。
Third conditional 总是表达遗憾吗？
不是。它也可以用于解释、批评、表达庆幸或推测过去的机会。
把“本来会”变成自然英语
用真实故事练习，对比不同结果，并在 ABA English 中让这一结构成为习惯。