U5Grammar 语法

1、if条件状语从句

if 引导的条件状语从句译为“如果……；假如……”, 表示在某种条件下某事很可能发生。

1）、句子结构为：“祈使句 + if条件状语从句”或“if条件状语从句 + 祈使句”。

Go and ask the policemen if you lose your way.

= If you lose your way, go and ask the policemen.

2）、句子结构为：“if条件状语从句 + 陈述句”或“陈述句 + if条件状语从句”

I won’t be a great football player if I go to college.

= If I go to college, I won’t be a great football player.

2、unless用法小结

连词unless意为“除非；如果不”，引导条件状语从句。

You’ll fail in Maths again unless you work harder.

You will never get anywhere unless you have set your goal.

unless引导的条件状语从句可以与if ... not进行转换。

I can’t buy a bike unless I have much money.

= I can’t buy a bike if I don’t have much money.

3、注意点：

 If it rains tomorrow, we will put off the sports meeting. ( 条件状语从句)

 We want to know if it will rain tomorrow. （宾语从句）

 I don’t know if he will come this week, if he comes, please tell me first. （宾语从句/ 条件状语从句）

Be careful , and you will succeed.

= If you are careful , you will succeed.

= If you are careless / aren’t careful, you will fail.

= Unless you are careful , you will fail.