条件句谈论如果某事为真会发生什么。你选择的时态表明你认为情况有多真实：事实、真实的可能性、想象的情况，或无法改变的过去。本主题有一个部分讲 真实 情况，两个部分讲 非真实 情况，另外两个部分两者兼有。本指南分为五个部分，与诊断测试的五个部分完全对应。
阅读英文版指南 → 本页为机器翻译，未经母语者审校，可能有不准确之处。以英文版为准。
你的诊断结果会告诉你哪个部分需要复习。请点击下面对应的部分。
核心思想：情况有多真实？
你选择的时态告诉读者你认为情况有多大可能。时态一变，同一个 if 句的意思就变了。
| 类型 | if 从句 | 结果 | 例句 |
|---|---|---|---|
| zero | 一般现在时 | 一般现在时 | If you heat ice, it melts. |
| first | 一般现在时 | will + base verb | If it rains, we will stay home. |
| second | 一般过去时 | would + base verb | If I had time, I would help. |
| third | 过去完成时 | would have + participle | If I had known, I would have called. |
| mixed | 过去完成时或一般过去时 | would or would have | If I had studied, I would be a doctor now. |
- 1
是事实，还是真的可能发生？ 用 zero 或 first 条件句。 是想象的吗？ 用 second 条件句（第 1 部分）。
- 2
两个半句各指现在还是过去？ 选择 second、third 或 mixed 条件句（第 2 部分）。
- 3
该用哪个连接词？ if、when、unless 或 in case，都用现在时表示将来（第 3 部分）。
时态表明说话人认为情况有多真实。第 4 部分用同样的思路处理愿望和遗憾，第 5 部分讲没有 if 的正式形式。
真实还是想象？
这是真实的可能性，还是只是想象？时态会告诉你。
规则： 时态表明情况有多大可能：真实的可能性和事实用 if 加现在时，后面接 will 或现在时；想象的情况用 if 加过去时，后面接 would。
同一情况，两种真实程度
| 含义 | 句型 | 例句 |
|---|---|---|
| fact (zero) | if + present simple, present simple | If you heat ice, it melts. |
| real possibility (first) | if + present simple, will + base verb | If I get the job, I will move to Busan. |
| imagined (second) | if + past simple, would + base verb | If I got the job, I would move to Busan. |
| advice | if I were you, I would | If I were you, I would apologize. |
正确说法
If it rains, we will stay home.
If I had more time, I would learn Spanish.
不要说
If it will rain, we will stay home.If I would have more time, I would learn Spanish.
这里 if 后面的一般过去时并不表示过去，而是表示说话人认为情况是想象的或不太可能的。
本部分的常见错误
- if 从句中用了 will
If the weather will be nice on Sunday, we will go hiking.✓ If the weather is nice on Sunday, we will go hiking.真实的计划在 if 后面用一般现在时。 - 条件句类型与意思不符
I don't have a dog, but if I have one, I would walk it every morning.✓ I don't have a dog, but if I had one, I would walk it every morning.想象的情况用一般过去时。 - 时态搭配错误
If you boil an egg for ten minutes, it would become hard.✓ If you boil an egg for ten minutes, it becomes hard.一般事实在两个部分都用一般现在时。
补充：if I was，以及 if 后面的 will
许多母语者在非正式口语中说 if I was you 。在书面语和考试中要用 were 。当 will 表示愿意（be willing）时，它可以跟在 if 后面，例如：If you will wait here, I’ll get the manager；或者当结果在时间上先发生时，例如：If it will help, I’ll stay late。
哪个时间？
两个半句各指现在还是过去？
规则： 让每个半句对应各自的时间：过去的条件用 had 加过去分词，现在的结果用 would 加动词原形，过去的结果用 would have 加过去分词。
把时间问题问两遍
| 条件 | 结果 | 句型 | 例句 |
|---|---|---|---|
| 现在 | 现在 | if + past simple, would + base verb | If I had a car, I would drive. |
| 过去 | 过去 | if + past perfect, would have + participle | If I had known, I would have called you. |
| 过去 | 现在 | if + past perfect, would + base verb | If I had studied medicine, I would be a doctor now. |
| 现在 | 过去 | if + past simple, would have + participle | If I were braver, I would have spoken up yesterday. |
留意 now、today、yesterday、last year 这类时间词，它们会告诉你每个半句需要哪种句型。Would 不能放在 if 从句中： If I would have known 是错的。
Would have、could have、might have
| 情态动词 | 含义 | 例句 |
|---|---|---|
| would have | 肯定的结果 | If I had left earlier, I would have caught the train. |
| could have | 可能的结果 | If I had left earlier, I could have caught the train. |
| might have | 不确定的结果 | If I had left earlier, I might have caught the train. |
本部分的常见错误
- if 从句中用了 would
If I would have seen the message, I would have replied.✓ If I had seen the message, I would have replied.if 从句用过去完成时，而不是 would have。 - mixed 条件句的句型错误
If I had taken the earlier flight, I would have been in Rome now.✓ If I had taken the earlier flight, I would be in Rome now.表示现在的结果需要 would 加动词原形。 - third 条件句的构成有误
If they had invited me, I would have went.✓ If they had invited me, I would have gone.would have 后面要接过去分词。
If、when、unless 和 in case
哪个词符合意思：if、when、unless 还是 in case？
规则： 在 if、when、unless、as long as 和 in case 之后，用一般现在时表示将来。预期会发生的事用 when，可能发生的事用 if，unless 表示 if not，in case 表示预防措施。
按意思选词
| 词语 | 含义 | 例句 |
|---|---|---|
| when | 你预期它会发生 | When the game ends, we’ll get dinner. |
| if | 它可能不会发生 | If the game ends early, we’ll get dinner. |
| unless | 如果不 | Unless you hurry, you will miss the bus. |
| as long as, provided that | 仅当 | You can borrow it as long as you bring it back. |
| in case | 作为预防措施 | Take an umbrella in case it rains. |
在所有这些词之后，都用现在时表示将来
| 从句引导词 | 例句 |
|---|---|
| when | I will call you when I get home. |
| as soon as | Tell me as soon as she arrives. |
| until, before, once | Wait until the light turns green. |
韩国和日本的学习者常把 if 用于必然发生的事，因为这两种语言用同一种形式表示两种意思。在英语中，预期会发生的事要用 when。
本部分的常见错误
- 混淆了 if 和 when
If I wake up tomorrow, I'll call you.✓ When I wake up tomorrow, I'll call you.起床是预期会发生的，所以用 when。 - if 从句中用了 will
Please wait here until the doctor will call your name.✓ Please wait here until the doctor calls your name.在 until 之后，用一般现在时表示将来。 - unless、wish 或其他替代形式用错了
Unless you don't book early, the hotel will be full.✓ Unless you book early, the hotel will be full.Unless 本身已经表示 if not。
愿望与遗憾
愿望或遗憾说的是现在还是过去？
规则： Wish 和 if only 谈现在时用过去时形式，谈过去时用过去完成时。Wish 加 would 表示抱怨别人的行为，it’s time 后面用一般过去时。
往后退一步
| 关于 | 句型 | 例句 |
|---|---|---|
| 现在 | wish + past simple | I wish I had more time. |
| 现在的能力 | wish + could | I wish I could sing. |
| 过去 | wish + past perfect | I wish I hadn’t sent that email. |
| 别人的行为 | wish + would | I wish you would turn the TV down. |
| 现在就该发生的事 | it’s time + past simple | It’s time we left. |
If only 和 wish 用法相似，但语气更强。不要对自己用 wish 加 would：要说 I wish I could，而不是 I wish I would。
本部分的常见错误
- unless、wish 或其他替代形式用错了
I wish I have a bigger apartment.✓ I wish I had a bigger apartment.关于现在的愿望用一般过去时。 - unless、wish 或其他替代形式用错了
I wish I didn't say that to my boss yesterday.✓ I wish I hadn't said that to my boss yesterday.关于过去的愿望用过去完成时。 - unless、wish 或其他替代形式用错了
I wish I would speak Chinese.✓ I wish I could speak Chinese.谈自己的能力，用 could，不用 would。
补充：would rather
I’d rather you didn’t tell anyone 也用一般过去时来谈现在。
正式的条件句
if 消失时，你还能认出条件吗？
规则： 正式英语可以省略 if，把 had、were 或 should 放在句首。但是 but for 加名词表示没有（without），otherwise 表示 if not，were to 会让将来的事听起来不太可能。
没有 if 的条件句
| 普通 | 正式 |
|---|---|
| If I had known, I would have called. | Had I known, I would have called. |
| If I were in charge, I would change it. | Were I in charge, I would change it. |
| If you need help, call us. | Should you need help, call us. |
| If it hadn’t been for the map, we would have gotten lost. | But for the map, we would have gotten lost. |
Otherwise 和 were to
| 形式 | 含义 | 例句 |
|---|---|---|
| otherwise | 如果不 | Leave now, otherwise you’ll be late. |
| if + were to | 不太可能的将来 | If the company were to close, many people would lose their jobs. |
这些形式常见于商务信函、通知以及雅思和托业等考试。在日常对话中，普通的 if 从句更常用。
本部分的常见错误
- 正式条件句的构成有误
If had we known about the delay, we would have waited.✓ Had we known about the delay, we would have waited.倒装省略了 if。 - 正式条件句的构成有误
But for you helped me, I would have failed.✓ But for your help, I would have failed.But for 后面接名词。 - 正式条件句的构成有误
Should you will need a taxi, ask at reception.✓ Should you need a taxi, ask at reception.在 should 之后，用动词原形。
自我检测
每个句子都正确吗？点击查看答案。如果你拿不准，部分标签会告诉你该看哪里。
第 1 部分If I see a good jacket in the sale, I will buy it.
正确。 真实的可能性：if 后用现在时，结果部分用 will。
第 1 部分If I would live by the sea, I would swim every day.
错误。 If I lived by the sea, I would swim every day. 不要在 if 之后用 would。
第 2 部分If we had taken a map, we wouldn't have gotten lost.
正确。 两个半句说的都是过去。
第 2 部分If she had gone to bed earlier, she would have felt better now.
错误。 If she had gone to bed earlier, she would feel better now. 表示现在的结果需要 would 加动词原形。
第 3 部分Take a jacket in case it gets windy on the boat.
正确。 In case 表示预防措施，后面用一般现在时。
第 3 部分I'll tell you the news when I will see you.
错误。 I’ll tell you the news when I see you. 在 when 之后，用一般现在时表示将来。
第 4 部分I wish I could remember her name.
正确。 表示现在能力的愿望用 could。
第 4 部分If only I listened to you last year!
错误。 If only I had listened to you last year! 谈过去，用过去完成时。
第 5 部分Were I you, I would take the job.
正确。 Were I you 是 if I were you 的正式说法。
第 5 部分Should you wanting more information, visit our website.
错误。 Should you want more information, visit our website. 在 should 之后，用动词原形。
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