条件状语从句
通常由以下连词引导：if,unless,on condition that,suppose,in case(如果,万一),as /so long as(只要)等 如：
①If you are thirsty,water far away can’t help you.
远水不解近渴.
②So long as we do not divorce ourselves from the masses,we are certain to be victorious.
只要我们不脱离群众,我们就一定会胜利.
③You can’t expect the reception to be clear unless the radio set is properly tuned it.
如果不把收音机调好,你不可能指望收到清晰的播音.
④Suppose we can’t get the necessary equipment,what shall we do?
假设我们弄不到必要的设备,那我们怎么办?
⑤We’ll let you use the room on condition that you keep it clean and tidy.
我们可以让你们用这个房间,如果你们能保持整洁的话.
⑥Send us a message in case you have any difficulty.
万一有什么困难请给我们一个信.
unless作连词,表示“如果不”,“除非”,在意义上等于if…not,在有些场合主要是指真实条件句,它引导的肯定式的条件状语从句可以和if引导的否定式的条件状语从句互换.
如：Unless you change your mind,I won’t be able to help you.
= If you don’t change your mind,I won’t be able to help you.
除非你改变你的想法,否则我不能帮助你.
unless不可用于假想的事情,因此,当if…not引导非真实条件状语从句时,一般不可改用unless.
如：
If she weren’t so silly,she would understand.
如果她不那么傻,她就会懂了.
