Unit 8 Grammar 语法知识+练习2025-2026学年人教版英语八年级上册

Unit 8 Grammar

If引导的【条件状语状语从句】

      一、 定义

If引导的条件状语从句，用来表示主句动作发生的前提条件，即从句表示条件。主句表示主要事件。常译为“如果......，就......”。（If引导的从句如果放在开头，一般需要用逗号与主句隔开。e.g. If you go there by bike, you will be late.）

 

      二、重要用法

1. 主句为以下情况之一时，条件状语从句用一般现在时：

（1）主句是一般将来时。

If it doesn’t rain tomorrow, we will go to the zoo.

（2）主句谓语部分含有情态动词（may, might, can, must, should等）。

If you eat bad food, you may fall ill.

（3）主句为祈使句。

If the light is red, wait for a minute.

 

2. 有些句子可与含if条件状语句互相转换。

（1）祈使句 + and / or + 陈述句。

Hurry up, or you’ll miss the train. = If you don’t hurry up, you’ll miss the train.

You will be healthier if you eat well. = Eat well and you will be healthier.

（2）借助with或without。

You can’t drive the car with the door open. = You can’t drive the car if the door is open.

If there is no water, fish will die. = Fish will die without water.

【主将从现】其他用法

1. 条件状语从句

引导词：if（如果）、unless（除非；如果不）、as long as（只要）

e.g.：You will make progress as long as you keep practicing English every day.

 

2. 时间状语从句

引导词：when（当......时）、as soon as（一......就......）、before（在......之前）、after（在......之后）、until/till（直到......为止）

e.g. I will send you a message as soon as I arrive at the airport.

 

Task 1：Read the following sentences and tell which part is main clause (主句) and which part is subordinate clause（从句）.

1. If you go there by bike, you will be late.

2. She will let me know me if he comes back.

3. If we ask people to bring food, they’ll just bring potato chips and chocolate.

4. If they have it today, half the class won’t come.

5. If you are ill, you must go to the doctor.

6. If it rains tomorrow, he’ll stay at home tomorrow.

 

Task 2：Fill in the blanks.

1. If it rains tomorrow, I_________(stay) at home.

2. He will take a trip to Beijing if he_________(be not) busy next week.

3. If you don't wear your school uniform to the party, the teachers ____________(not let) you in.