不定式是非谓语动词的重要情形之一。由于它具有名词、动词、形容词和副词的多种特征，所以在句中可以作主语、宾语、表语、状语、宾语补足语、主语补足语、同位语或独立成分。不定式作定语时兼有主动式和被动式两种形式，现归纳如下：

一、不定式作定语只能用主动式的情形

1.不定式所修饰的名词和不定式中的动词所表示的动作是逻辑上的主谓关系（此时，该不定式短语可转化为一个定语从句）。例如：

Li Xuemei was the first athlete to get to the finishing line（=... athlete who got to the finishing line）.李雪梅是第一个到达终点的选手。

We need someone to help to repair the computer（=...someone who will help to repair the computer）.我们需要一个能帮助我们修电脑的人。

He is always the first to bear hardships（=...the first who will bear hardships），the last to enjoy comforts（=the last who will enjoy comforts）. 他总是一个吃苦在前，享乐在后的人。

2.不定式与它修饰的名词是逻辑上的动宾关系，且主语是不定式中的动词所表示动作的逻辑主语或在句中能找到其逻辑主语。例如：

He has a lot of work to do today.今天他有大量的活要干。

Do you have anything more to say？你还有什么话要说吗？

Our teacher arranged us six exercises to do at home.老师给我们安排了六道练习题在家里做。（us是to do的逻辑主语）

Father always bought his son some toys to play with after his business.父亲每次出差回来都给他的儿子买玩具玩儿。（son是to play with的逻辑主语）

3.有些句子中，尽管行文上没有不定式的逻辑主语，但是从句意角度可以体会出不定式中隐含着“for sb.to do”结构。此时，不定式应该用主动式。例如：

There is nothing（for us） to worry about.没有什么可值得担忧的。

That will be the only thing（for us）to do now.这恐怕是目前（我们）唯一可行的办法。

It is a good opportunity（for us/them）to learn from the farmers.这可是一个向农民学习的大好机会。

4.部分形容词，如eager，anxious，determined，able等，其后常跟不定式，他们的同源名词后要用不定式的主动式作定语。例如：

（Mr.Smith was eager to get back to teach at the school.）

Mr.Smith\'s eagerness to get back to teach at the school was quite obvious.史密斯先生急于回校教学这一点是显而易见的。

（He was anxious to know the results of the test.）

We could see his anxiety to know the results of the test.我们看得出他很想知道这次测验的结果。

（They were determined to catch up withus.）

In their speech they expressed their determination to catch up with us.他们在讲话中表达了他们要赶上我们的决心。

5.部分动词，如attempt，promise，plan， intend，refuse等，其后常跟不定式作其宾语，它们的同源名词后要用不定式的主动式作定语。例如：

（They attempted to reach there before five o\'clock.）

They failed in their attempt to reach there before five o\'clock.他们试图在五点以前赶到那里，但是没有办到。

（You promised to give me a present on my birthday.）

You haven\'t kept your promise to give me a present on my birthday.你没有遵守在我过生日时给我礼物的诺言。

以上就是今天分享的全部内容了，希望本文对各位有所帮助，预祝各位取得满意的成绩，如需了解更多相关内容，请关注帮考网！