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unless和if not引导的否定条件句

作者: admin来源: 网络文章 时间: 2019-09-04

两者都可表示否定的条件,有时可换用。如:

Come tomorrow unless I phone [if I don't phone]. 要是我没有打电话,明天就来。

You won't catch the train unless you hurry [if you don't hurry]. 你要是不赶快,你就赶不上火车了。

但是在下列情况下,通常要用 if ... not 而不用 unless:

1. 当从句所引出的情况不是表示主句情况发生的一种例外而只是一种可能,并且这种可能正是导致主句情况发生的主要原因时,英语习惯只用if...not,不用unless。如:

I'll be surprised if he doesn't win. 如果他不赢,我会感到惊奇。

She'd look nicer if she didn't wear so much make-up. 要是她不过分打扮,本来会更好看的。

I'll be sorry if they do not come tomorrow. 如果他们明天不来,我将感到非常遗憾。

2. 当从句内容与已知事实相反时(即引出虚拟条件时),通常要用if...not,而不用unless。如:

If he weren't so silly, he would understand. 他要不是那样傻的话,他就会明白了。(实际上他很傻)

If I hadn't stopped her, she would have jumped down. 要不是我阻止了她,她就跳下去了。(实际上我阻止了她)

unless有时可引出一个过去未曾实现的假想法情况,对前面主句进行补充说明(此时必须置于主句之后,且前面常用破折号而不用逗号)。如:

I couldn't have got to the meeting on time—unless I had caught an earlier train. 我不可能及时赶到会场,除非我赶上了较早一班火车。(事实是“我”没有及时到会)

此句若将unless改为if...not,则成为:

I couldn't have got there If I hadn't caught an earlier train. 如果我没赶上较早一班火车,我就不能到达那儿了。(事实是“我”及时到会了)

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