英语中的动词不定式具有副词的功能,可以在句子中作状语,表示多种意义.在这里就动词不定式作目的状语进行单独讨论.
一、不定式和不定式短语作目的状语
不定式和不定式短语作目的状语,主要用来修饰动词,表示某一动作或状态的目的.为了使目的意义更加清楚或表示强调意义时,还可以在前面加 in order to 或 so as to.例如：
I've written it down in order not to forget.
He shouted and waved so as to be noticed.
在句子中作谓语动词的状语的不定式或不定式短语,表示的是主语的目的,因此,其逻辑主语通常是句子的主语.比较：
To draw maps properly,you need a special pen.(正)
To draw maps properly,a special pen is needed.(误)
由 in order to 引导的目的状语,既可以置于句尾,也可以置于句首,而由 so as to 引导的目的状语,只能置于句尾,而不能置于句首.比较：
They started early in order to get there in time.(正)
In order to get there in time,they started early.(正)
They started early so as to get there in time.(正)
So as to get there in time,they started early.(误)
二、不定式的复合结构作目的状语
当不定式或不定式短语有自己的执行者时,要用不定式的复合结构(即在不定式或不定式短语之前加 for + 名词或宾格代词)作状语.例如：
He opened the door for the children to come in.
She fetched several bottles which she placed on the counter for Harry to inspect.
三、目的状语从句与不定式的转换
英语中的目的状语从句,还可以变为不定式或不定式短语作状语,从而使句子在结构上得以简化.可分为两种情况：
1.当目的状语从句中的主语与主句中的主语相同时,可以直接简化为不定式或不定式短语作状语.例如：
We'll start early in order that/so that we may arrive in time.
We'll start early in order to/so as to arrive in time.
2.当目的状语从句中的主语与主句中的主语不相同时,要用动词不定式的复合结构作状语.例如：
I came early in order that you might read my report before the meeting.
I came early (in order) for you to read my report before the meeting.