1.用不定式表达时要求不定式动作的执行者必须是句子的主语，固定结构有：

　　(1) to do sth.

　　To make himself heard，he stood up and shouted at the top of his voice.

　　This weekend party is designed to make life happy for the students.

　　(2) in order to do sth.

　　We turned the lights off in order not to waste electricity.

　　They will water the little plants in order to stop the soil from getting too dry.

　　(3) so as to do sth. (不能位于句首)

　　否定形式只能用in order not to do sth.或 so as not to do sth.。而not to do sth. 意为“不是为了……”。

　　He kept on saying the name aloud so as not to forget it.

　　He hurried in order not to be late for class.

　　He came not to ask for the information (他来不是为了打听消息).

　　2. 用从句表示，此时主句的主语可以一致，也可以不一致，固定句型有：

　　(1) so that + 从句(从句中常有情态动词can, could, may, might等)

　　He studied very hard this term so that he could catch up with his deskmate.

　　We use new methods so that we can do the job quickly and cheaply.

　　(2) in order that+从句(从句中常用情态动词can，could，may，might加动词原形)

　　The boy left without breakfast in order that he could get to school before classes.

　　(3) in case以免；以防(从句中常用一般现在时)

　　Take your umbrella in case it rains.

　　(4) for fear that 以免；以防

　　He took an umbrella with him for fear that it might rain.

　　一定要注意，用不定式结构时，其逻辑主语(动作的执行者)必须是句子的主语。用从句结构时逻辑主语(动作执行者)是不是句子的主语均可。

　　3. 目的表达的其它方式：

　　(1) for / with the purpose of doing sth.

　　Did you come to London for / with the purpose of seeing your family，or for your business purposes?

　　(2) do sth. for sth. (=do sth. to get sth.)

　　Soon after he got to school，he hurried back home for his English books.

　　(3) What... for?

　　What do you want a science lab for?

　　(4) The purpose of (doing) sth. is to do sth.

　　The purpose of new technologies is to make life easier not to make it more difficult.

　　(5) go / come to do sth. =go / come and do sth.

　　He came specially to say sorry to you.

　　(文/冯欣； 英语辅导报新课标高一版 04~05学年度第24期；版权归英语辅导报社所有，独家网络合作伙伴新浪教育，未经许可，不得以任何形式进行转载。)