■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(from www.yygrammar.com)：
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。
