职称英语指导:语法知识——名词性从句(3)
文章出处： 发布时间：2006-07-09
4. 条件状语从句引导条件状语从句的连词有：if，unless，as / so long as，suppose （that），supposing （that），in case，when等。条件状语从句可以分为真实条件状语从句和非真实条件状语从句。
⑴真实条件句真实条件句表示现实或可能的情况，由if引导，它的主句可以是陈述句，疑问句或祈使句，可置于主句之前或之后。
If you heat ice，it melts. If it rained，I went by bus. unless引导的否定条件状语从句，在意义上相当于if…not，如：
Don‘t come unless I telephone. as / so long as，provided / providing （that）意为“只要、如果”，如：
You can borrow this pen as long as you can keep it well. in case在英国英语中表示目的，在美国英语中可表示条件，意为“如果、万一”，如：
In case the house burns down，we‘ll get the insurance money.
⑵非真实条件句请参阅第十一章“虚拟语气”。
5.让步状语从句引导让步状语从句的连词有：although，though，even if，even though，if，for all that，when，while，whether…or，whatever，no matter what等。
although和though意义一样，都作“虽然、即使”解，都表示让步，一般情况下可互换使用，只是although语气较重，大多置于句首。如：
They are generous though they are poor. Although he was Japanese，he spent most of his life in China. even if和even though都作“即使”解，两者可以互换使用，如：
She insisted on her own opinion even though / even if he was wrong. if作“即使、虽然”解，也表示让步，如：
If he is wrong，he is honest. whether…or作“不论……是否”或“不论……还是”解，如：
You don‘t have to worry me whether I am well or ill.为了强调让步意义，在正式文体或文学作品中，常用as引导让步从句，从句的补语或状语置于句首。如：
Tall as he was，he couldn‘t reach the top of the shelf. Strong as you may be，you cannot lift it.词尾为-ever的wh-词可以与“no matter + wh-词”互换使用，作“无论……”解，后者常用于口语中，如：
Whoever / No matter who rings，tell him I‘m out. Wherever / No matter where he is，he will be thinking of you.由whenever，wherever，however引导的从句，也可以分别看作时间状语从句、地点状语从句和方式状语从句。把它们当作让步状语从句是因为它们常有no matter when （where，how）的含义。
6.原因状语从句原因状语从句通常由because，since，as，when now （that），seeing （that），considering （that）等引导。
because，since和as三者的区别如下：
because的语势最强，其次是since，再次是as. because可以回答why引导的特殊问句，而since和as不能。
because引导的从句可以被just，only，simply等副词修饰，也可以用并列连词构成并列的because从句，而since和as则不能。如：
We pardoned him only because he was still young. for表示原因时，作“因为”解，多用于正式文体，有时可以与because换用，但for从句只能置于主句之后。如：
She didn‘t go to school，for / because she was ill. now （that）和seeing （that）都作“既然”解，通常可与since或as换用，如：
Now （that） you have come，you may as well stay. Seeing （that） he is inexperienced，he is not fit for the work. 7. 结果状语从句引导结果状语从句的连词有：so that，so…that，such that，such…that，that等。
当从句前面有逗号时，so that中that可省略，如：
It was dark，so （that） we could see nothing in front of us.“So + 形容词 / 副词 + that”是引导结果状语从句的常用结构，如：
He talked so loud that he annoyed the speaker. He was so brilliant that he made a lot of inventions.“such （a） + 形容词 + 名词 + that”与“so…that”的意义相同，如：
It was such a hot day that people could not go out. He painted such beautiful pictures that the visitors were lost in admiration. that可以单独引导结果状语从句，如：
The question is of great importance that it cannot be neglected. 8. 目的状语从句引导目的状语从句的连词有：in order that，so that，so，that，in case，for fear that，lest等。
in order that与so that的意义和用法基本相同，in order that多用于正式文体，常表示经过认真考虑的目的，如：
In order that he would have more space for painting，he bought a big house. You ought to write to him，in order that he won‘t feel we are hiding things from him. So和that可视为so that的省略形式，但不如so that常用，如：
Bring it closer so / that I may see it better. for fear that，in case和lest都表示否定的目的，相当于so that…not或in order that…not，作“以免、以防”解。
He wrote the name down for fear that he should forget it . lest限于正式文体，它所引导的从句中的谓语动词多用should be型或be型虚拟形式，如：
He hid the box lest it （should） be stolen. in case引导的从句谓语既可以用虚拟形式，又可用陈述语气，如：
Better take more clothes in case it is cold. She doesn‘t dare to go out in case she is recognized / （should） be recognized.
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