目的状语从句
从句部分是用以补充说明主句中谓语动词发生的目的的状语从句。表示目的状语的从句可以由that, so that, in order that, lest, for fear that, in case等词引导；目的状语从句的谓语常含有may, might, can, could, should, will, would等情态动词。
例句
Say it louder(so)that everyone can hear you.
大声说，以便大家都能听到你。
I am telling you that lest you should make a mistake.
我告诉你这一点，以免你搞错。
I got up early so that I could catch the first bus.
我起得很早，目的是为了赶上头班公共汽车。
She worked hard so that everything would be ready by 5 o'clock.
她努力工作，以便在五点前是一切都就绪。
She looked down so that she should not see his eyes.
她垂下目光，使她看不到他的眼睛。
We'll sit nearer the front so we can hear better.
我们坐的靠前一点，因此，我们听得清楚一点。
He works hard in order that his family may be happy.
为了让家人幸福，他努力工作。
He shouted at the top of his voice,to the that（=in order that）he might be heard.
他高声呼喊，为的是让人们能听见他的说话。
I am punishing the child lest he should make the same mistake.
我惩罚那个孩子，以免他再犯同样的错误。
She took her umbrella lest it（should）rain.
他带了把雨伞，唯恐天要下雨。
Lest the wall（should）collapse,they evacuated the buliding.
他们撤离了大楼，以防墙壁倒塌。
Speak clearly so that they may understand you.
讲清楚些，以便他们能理解你。
He studied hard in order that he could pass the exam.
他努力学习以便能考试及格。
Shut the window for fear that it may rain.
把窗子关上以防下雨。
引导目的状语从句的从属连词
主要的有 in order that, so that, in case, for fear等：
Speak clearly so that they may understand you.
讲清楚些，以便他们能理解你。
He studied hard in order that he could pass the exam.
他努力学习以便能考试及格
Shut the window for fear that it may rain.
把窗子关上以防下雨。
【注】so that 引导目的状语从句时有时可省略so而只用that，有时也可只用so：
Bring it closer that I might see it better.
拿近些，使我能看得清楚些。
I’ll show you so you can see how it’s done.
我将做给你看，以便你知道应怎样干。
目的状语从句与状语短语的转换
为了简洁起见，当目的状语从句的主语与主句的主语相同时，目的状语从句有时可用表目的的不定式短语替换：
He got up early so that he could catch the early bus. / He got up early so as to catch the early bus.
他起床很早以便赶上早班车。
He came in quietly in order that he shouldn’t wake his wife. / He came in quietly in order not to wake his wife.
他轻轻进来，以免把他妻子吵醒。
有时还可与表示目的的介词短语替换：
He left an hour early for fear he might miss the train. / He left an hour early for fear of missing the train.
他提前一小时离开，以免错过火车。
一点注意
in case既可引导目的状语从句，也可引导条件状语从句，主要视句意而定：
In case he comes, let me know.
如果他来，告诉我一声。
Tell me in case you get into difficulty.
遇到困难请告诉我。
【注】in case引导目的状语从句，从句有时可用“should+动词原形”这样的形式：
Take your coat in case it rains (should rain).
带着雨衣以防下雨。
参考资料