the last 引导的定语从句（TheZeroConditional）

the last 引导的定语从句（TheZeroConditional）IF clause条件句由两个组成部分：IF从句 主句。四大类型条件句均使用连词IF。2 – The Second Conditional 第二类条件句3 – The Third Conditional 第三类条件句Each conditional sentence has an IF clause and a main clause. And all the four types of conditionals use the conjunction IF.

In English there are four types of conditional sentences:

英语中有四大类型条件句：

0 – The Zero Conditional 零条件句

1 – The First Conditional 第一类条件句

2 – The Second Conditional 第二类条件句

3 – The Third Conditional 第三类条件句

Each conditional sentence has an IF clause and a main clause. And all the four types of conditionals use the conjunction IF.

条件句由两个组成部分：IF从句 主句。四大类型条件句均使用连词IF。

	IF clause IF从句	Main clause ★ If you heat water it evaporates. ★ 如果你加热水，水就会蒸发。
1st	IF present simple IF 一般现在时	will infinitive will 动词不定式	to talk about possible and likely future outcomes 谈论将来可能发生的情况
★ If you study hard you will pass the exam. ★ 如果你努力学习，你将通过考试。
2nd	IF past simple IF 一般过去时	would infinitive would 动词不定式	to talk about improbable or impossible situations in the present or future 谈论现在或将来不可能发生的情况 与现在事实相反（非真实条件句）
★ If I won the lottery I would buy a big house. ★ 如果我中了，我会买一栋大房子。
3rd	IF past perfect IF 过去完成时	would have past participle would have 过去分词	to describe an event for the past that did not happen 描述过去未发生的事情 与过去事实相反（非真实条件句）
★ If I had studied harder I would have passed the exam. ★ 如果我当时更努力地学习，我早就通过考试了。

The IF clause gives us the condition or situation and the main clause gives us the result. The Zero and the First Conditional express real or possible conditions and results. The Second and the Third Conditional express impossible hypothetical unreal conditions and results.

IF从句提供条件或情况，主句描述产生的结果。零条件句和第一类条件句描述真实或可能发生的条件和结果。第二类条件句和第三类条件句描述不可能发生的、假设的、不真实的条件和结果。

With all conditional sentences the order of these clauses is not fixed. So you can swap them around. And even when you change the order of the clauses the meaning is the same. In writing if your IF clause comes first add that comma. If your main clause comes first you don’t need a comma.

在所有类型的条件句中，IF从句和主句的顺序可以互换。即使句子的顺序发生改变，其含义也不会发生变化。在书写中，如果把IF从句放在句首，中间加个逗号，再加主句。如果主句放在句首，则无需加句号。

If I practice I will get better.

I will get better if I practice.

The Zero Conditional 零条件句

◆ A Zero Conditional sentence consists of two present simple verbs. Both parts of the sentence are in the present tense.

零条件句的IF从句和主句均由一般现在时的动词引导。

If this thing happens that thing happens.

IF 一般现在时， 一般现在时

◆ We use the Zero Conditional to talk about permanent truths such as scientific facts and general habits.

谈论客观真理，如科学事实，和一般的习惯。

★ If you heat water it evaporates.

如果你加热水，水就会蒸发。

★ If you leave ice cream in the sun it melts.

如果你把冰激凌放在太阳下，它就会融化。

★ People die if they don’t drink enough water.

如果人们不喝足够多的水，就会死亡。

★ If you put a stone in water it sinks.

如果你把石头放在水里，它就会沉下去。

★ If you eat a lot you put on weight.

如果你吃得多，你就会发胖。

You can usually replace IF with WHEN OR WHENVER without the meaning changing.

这里的IF可以用WHEN OR WHENVER替代，而不会改变其意义。

◆ We often use the Zero Conditional to give instructions with the imperative in the main clause.

"零条件句 "可以用来发出指令，主句使用祈使句。

★ Text me if you get lost.

如果你迷路了，就给我发短信。

★ If you accidently drop some trash pick it up.

如果你不小心掉了一些垃圾，就把它捡起来。

★ If Mary calls don’t answer the phone.

如果玛丽打电话来，不要接电话。