Section Ⅱ　Grammar--条件状语从句；让步状语从句

[思维导图]

一、条件状语从句

条件状语从句是用于表示主句动作发生的前提或条件的从句。通常由下列从属连词和短语来引导：if(如果，假如)，unless(除非)，as(so) long as(只要)，provided/providing(that)(只要)，suppose/supposing(假设)，on condition (that)(如果)，in case(以防)等。

We'll come over to see you on Wednesday if we have time.

如果有空，我们星期三来看你。

You can borrow my car as long as you promise not to drive too fast.

你可以借用我的车只要你承诺不开快车。

I'll let you have the book on condition that you return it to me next week.

我可以把书借给你，条件是你下星期得还给我。

Take an umbrella with you in case there is rain this afternoon.

随身带着把伞，以防今天下午下雨。

[温馨提示]

(1)在条件状语从句中，用一般现在时代替一般将来时，一般过去时代替过去将来时。

If he arrives tomorrow，I will be waiting for him at the airport.

如果他明天到，我将在机场等他。