Intro

类型	If clause	Main clause	Examples
0(客观)	present simple	present simple	If pilots use checklists, why don’t doctors use them?
1st(客观)	present simple	future tense	If it’s sunny tomorrow, we’ll go on a picnic.
2nd(对现在虚拟)	past tense	would(n’t) + infinitive	If I had surgery, I would want the surgeon to use checklists.
3rd(对过去虚拟)	past perfect	would(n’t) + have done	If they’d worn their masks, the patient wouldn’t have been infected.

0条件句

Zero Conditionals

表示只要满足了某个条件，总会出现某种现象或导致某种结果，通常用于表示经过验证的科学理论、规则等。

句型：if/when + 一般现在时 , 一般现在时.

If you heat water to 100 degrees, it boils.
If I drink too much coffee, I can't sleep at night.
Ice melts if you heat it.
When the sun goes down, it gets dark.

第1条件句

First Conditionals , 也称“真实条件句”。

用于表示未来可能会发生或成为现实的条件或假设，遵循主将从现的原则。

句型：if/when + 一般现在时 >> will + 动词原形

It it rains tomorrow, we'll have to put off the sports meeting.
Arsenal will be top of the league if they win.
When I finish work, I'll call you.

条件句经常使用unless, as long as, as soon as 或 in case 替代 if 。

I'll leave as soon as the babysitter arrives.
I don't want to stay in London unless I get a well-paid job.
I'll give you a key in case I'm not at home.
You can go to the party, as long as you're back by midnight.

第2条件句

Second Conditionals

用于描述一个想象中的现在或将来的情况，这个情况在现实中无法或很难实现。

If we had a garden, we could have a cat. 如果我有个花园，我就可以养猫了。（我没有花园）
If I won a lot of money, I'd buy a big house in the country. 如果我有钱，我就可以买个大房子。（我没有钱）
I wouldn't worry if I were you. 如果我是你我就不担心。（我不是你）

通常句型：if + 一般过去时 >> would + 动词原形

如果if后面连接be动词，那么 if I were, if he were, if she were and if it were语法上来说正确。

但是，通常会听到用was，特别是主语为he/she的时候。

If I were you, I wouldn't mention it. 如果我是你，我不会提起这个。（我不是你）
If she was prime minister, she would invest more money in schools. 如果她是首相，她会给学校更多投资。（她不是首相）
He would travel more if he was younger. 如果他年轻一些，他会去更多地方旅游。（他不会变年轻）

第3条件句

Third conditional

用于表示与过去事实相反的条件或假设。

通常句型：if + 过去完成时 >> would have + 过去分词

If I had followed his advice, my girlfriend wouldn't have left me. 如果我当初听从了他的建议，我女朋友就不会离开了。（事实上我没听他的建议，我的女朋友也已经离开了我。）
If I had understood the instructions properly, I would have passed the exam. 如果（当时）我清楚的理解那些指令，我就能通过考试了。
We wouldn't have got lost if my phone hadn't run out of battery. 如果（当时）我的手机电池没用完，我们就不会迷路了。

混合（错综）条件句

过去的条件/情况对现在的结果

这种混合条件句论及过去的一个不真实的情况，以及该情况在现在可能会有的结果。这些句子表达的情况与过去和现在的事实都是相反的。在这类混合条件句中，if 子句的时间指的是过去，而主要子句的时间指的是现在。

If I had studied I would have my driving license.（但我没有努力准备，而且现在还没有驾照）
I would be a millionaire now if I had taken that job.（但我没有接下那份工作，现在我也不是百万富翁）
If you had spent all your money, you wouldn't buy this jacket.（但你没有花掉所有的钱，现在你可以买下这件夹克）

现在或持续的情况对过去的结果

这些混合条件句论及现在的一个不真实的情况，以及该情况在过去可能会有的结果（但只是虚设）。在这些混合条件句，if 子句的时间指的是现在或随时，而主要子句的时间指的是过去。例如：「If I wasn't afraid of spiders」（要是我不怕蜘蛛）与现在事实相反，事实上是「我怕蜘蛛」。而「I would have picked it up」（我早就会捡起它了）也是与过去事实相反，实际上我并没有捡起来过。

If she wasn't afraid of flying she wouldn't have travelled by boat.
I'd have been able to translate the letter if my Italian was better.
If I was a good cook, I'd have invited them to lunch.
If the elephant wasn't in love with the mouse, she'd have trodden on him by now.

其他

I wish和If only

Rule: To talk about how we would like things to be different now or in the future, we often use I wish (我希望) or if only (如果…就好了) and the past tense.

I just wish I could disappear. / If only someone understood me.

Rule: To talk about regrets we have about things we did in the past, we often use: I wish or if only and the past perfect tense.

If only I had studied harder for that test. / I wish I hadn’t say those things to my parents.

I would prefer to / it if, It’s time, I’d rather/sooner

Rule:

It’s (high) time + subject + past simple 是某人干某事的时候了
I’d rather / sooner + base form
I’d prefer + infinitive
I’d prefer / sooner + subject + past tense
I’d prefer it if + subject + past tense

It’s about time you got out of bed and did something.
I’d sooner go to the park and play football for real.
I’d prefer to take a taxi.
I’d rather you didn’t practice right now.
I’d prefer it if you didn’t keep taking my things.