条件状语从句的特征

条件状语从句：表示条件或要求性质的状语从句
例句：
1）I can lend you the bike on condition that you return it on time我可以把自行车借给你，但条件是你必须限期归还(on condition that you return it on time是条件状语从句)
2）You'll fail if you don't work hard如果你不努力就会失败(if you don't work hard是条件状语从句)
引导词有：if,unless,so(as)long as,on condition that(只要）等

连接词主要有 if, unless, as/so long as, on condition that 等。.
if 引导的条件句有真实条件句和非真实条件句两种。非真实条件句已在虚拟语气中阐述。

unless = if not.
Let's go out for a walk unless you are too tired.
If you are not too tied, let's go out for a walk.

典型例题
You will be late ___ you leave immediately.
A. unless B. until C. if D. or
答案A。 句意：除非你立即走，否则你就回迟到的。可转化为 If you dong leave immediately, you will be late. B、D句意不对，or表转折，句子如为 You leave immediately or you will be late.

引导条件状语从句最常用的连词是if,由if引导的条件状语从句表示在某种条件下某事很可能发生。如:

If you ask him, he will help you.如果你请他帮忙,他会帮你的。

If you fail