VOA一分鐘英語(yǔ)：第三類(lèi)條件句用法總結(jié)

英語(yǔ)中的條件句用來(lái)對(duì)過(guò)去、現(xiàn)在或?qū)?lái)發(fā)生的事情或情況作出假設(shè)。在對(duì)過(guò)去的情景作出假設(shè)、假想時(shí)，應(yīng)該使用 “第三類(lèi)條件句（the third conditional）”。這類(lèi)句子的典型結(jié)構(gòu)是：“If + 主語(yǔ) + 過(guò)去完成時(shí)，主語(yǔ) + would have + 過(guò)去分詞”。
 
Welcome to BBC Learning English. I'm Sam and today we're talking about the third conditional.
The third conditional is a little strange because we're talking about something that didn't happen in the past. Why would we do that? Well, because sometimes we want to imagine a different outcome.
A friend of mine came to visit me yesterday. It was a surprise, so when I opened my front door, I said: "If I'd known you were coming, I would have baked a cake!"
Did I know she was coming? No. Did I bake a cake? No.
So I'm imagining a different result.
Because we're talking about an imaginary past, we use:
If + the subject + the past perfect, the subject + would have + past participle
And you can also swap those round: What would you have done if you'd known your friend was coming?
 
用法總結(jié)
1 句式
典型的第三類(lèi)條件句的句式如下：
If + 主語(yǔ) + 過(guò)去完成時(shí)，主語(yǔ) + would have + 過(guò)去分詞
這個(gè)句式的前半部分（If + 主語(yǔ) + 過(guò)去完成時(shí)）被稱(chēng)作 “條件從句” 或 “if 從句”；后半部分（主語(yǔ) + would have + 過(guò)去分詞）被稱(chēng)作 “主句”。條件從句（if 從句）和主句之間的順序可以互換，意思不變。主句在前時(shí)，主句和從句之間不使用逗號(hào)。
If I'd known you were coming, I would have baked a cake.
I would have baked a cake if I'd known you were coming.
 
2 用法
第三類(lèi)條件句被用來(lái)對(duì)過(guò)去不曾發(fā)生的事情作設(shè)想。條件從句（if 從句）對(duì)過(guò)去作設(shè)想，主句講述設(shè)想的結(jié)果。
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?