在复合句中，由从句表示的状语叫做状语从句。它可以用来修饰主语中的动词.形容词.副词等。根据它表达的意思，状语从句可以分为时间状语从句，地点状语从句，条件状语从句，比较状语从句，目的状语从句，结果状语从句和让步状语从句等。由连接词if或unless引导的状语从句叫做条件状语从句。（注意：在含有条件状语从句的复合句中，如果主句是一般将来时态，从句要用一般现在时[主将从现原则])
经典语句：If it doesn't rain tomorrow, we will go to the zoo.
If you open the door，I will come in.
条件状语从句就是用以表示“在某种条件下,会……”。常用if ,in case , on condition等词来引导，连接词主要有 if, unless, as/so long as, on condition that, provided, suppose, supposing 等。主句用一般将来时，if或unless引导的条件状语从句用一般现在时。
固定搭配：unless = if...not.
e.g. Let's go out for a walk unless you are too tired.
If you are not too tired, let's go out for a walk.
if 引导的条件句有真实条件句和非真实条件句两种:
真实条件句，
如：If it rains tomorrow, we won’t go on a picnic.
非真实条件句是虚拟语气的一种，表示与事实相反，如：
If I were you, I would go with him.
so/as long as只要
由as (so) long as, in case引导。
So long as you’re happy, it doesn’t matter what you do.
只要你高兴，你做什么都没有关系。
You may borrow my book as long as you keep it clean.
只要你保持书的清洁，你就可以把我的书借去。
Take your umbrella in case it rains.
带着你的伞吧，以防下雨。
【练一练】
用括号内所给动词的适当形式填空。
1. If you (get) up early tomorrow morning, you (catch) the early bus.
2. If he (be) free this weekend, he (visit) his grandparents.
3. ―I don’t know if he (come) to the party.
―Don’t worry. If he (come), I will let you know first.
4. (leave) it for me if Mary (not want) to do it.
Keys:
经典语句：If it doesn't rain tomorrow, we will go to the zoo.
If you open the door，I will come in.
条件状语从句就是用以表示“在某种条件下,会……”。常用if ,in case , on condition等词来引导，连接词主要有 if, unless, as/so long as, on condition that, provided, suppose, supposing 等。主句用一般将来时，if或unless引导的条件状语从句用一般现在时。
固定搭配：unless = if...not.
e.g. Let's go out for a walk unless you are too tired.
If you are not too tired, let's go out for a walk.
if 引导的条件句有真实条件句和非真实条件句两种:
真实条件句，
如：If it rains tomorrow, we won’t go on a picnic.
非真实条件句是虚拟语气的一种，表示与事实相反，如：
If I were you, I would go with him.
so/as long as只要
由as (so) long as, in case引导。
So long as you’re happy, it doesn’t matter what you do.
只要你高兴，你做什么都没有关系。
You may borrow my book as long as you keep it clean.
只要你保持书的清洁，你就可以把我的书借去。
Take your umbrella in case it rains.
带着你的伞吧，以防下雨。
【练一练】
用括号内所给动词的适当形式填空。
1. If you (get) up early tomorrow morning, you (catch) the early bus.
2. If he (be) free this weekend, he (visit) his grandparents.
3. ―I don’t know if he (come) to the party.
―Don’t worry. If he (come), I will let you know first.
4. (leave) it for me if Mary (not want) to do it.
Keys:
