不定式的一般式表示的动作通常与主要谓语的动作同时或几乎同时发生，或是在它之后发生。

 他看起来好像很高兴。He appears to be very happy  

 为了赶上火车，我们最好赶紧乘出租车去车站。to catch the train we'd better hurry to the station by taxi  

不定式的进行式表示正在进行的或与谓语动词同时发生的动作。

 我到达那里的时候，天碰巧在下雨。it happened to be raining when I got there  

 我很高兴和你一起旅游。I'm glad to be traveling with you  

不定式的完成式表示的动作在谓语表示的动作之前发生。

 我很抱歉把你的钥匙弄丢了。I'm sorry to have lost your key  

 我本来想昨晚完成工作的，但是我感觉身体不舒服。I meant to have finished my work last night but I didn't feel very well  

 对我来说，被邀请来你们国家是一件很荣幸的事情。it has been an honor for me to have been invited to your country  

不定式的完成进行式表示的动作在谓语之前发生并且一直进行着。

 据说他在伦敦一直住了二十年。He was said to have been living in London for twenty years  

 很抱歉，我一直打扰你。I'm sorry to have been interrupting you  

 据说他正在国外读书。He is said to be studying abroad  

不定式的进行式表示动作正在进行

 据说他在国外学习过。He is said to have studied abroad  

不定式的完成式表示动作已经结束

一般式 to be done

 这些是要发给学生的书。These are the books to be given out to the students  

 他要求被派往最需要他的地方。He asked to be sent to the place where he was most needed  

完成式 to have been done

 据说这部小说已被译成多种语言。The novel is said to have been translated into many languages  

 看起来他已经被询问过很多次了。He appeared to have been questioned for many times  

不定式的否定形式由 not 或 never 加不定式构成。

 由于天气不好，我们决定不出去。We decided not to go out because of the bad weather  

 从不犯错是不可能的。Never to have made any mistake is impossible  

谓语动词的否定和不定式的否定不同的意义

 我没有答应叫醒他。I did not promise to wake him up  

 我答应了不叫醒他。I promised not to wake him up  

不定式短语在句首作主语

 人贵有自知之明。to know oneself is difficult  

 说是一回事，做又是另一回事。to say is one thing and to do is another  

 爱与被爱是一个人能获得的最大幸福。to love and to be loved is the greatest happiness one can get  

在很多情况下，人们通常用 it 作为形式上的主语，而把不定式移到谓语之后，使句子结构显得平稳一些。

 背对着老师，拒绝回答问题是不礼貌的。it 's rude to turn your back to your teacher and refuse to answer  

 想不下苦功就能学会外语是不可能的。it is impossible to learn a foreign language without making painstaking effort  

 浪费了这么多时间，真是遗憾。it seemed a pity to have wasted so much time  

当主语和表语都是不定式时，不能用形式主语代替动词不定式。

 尊重别人就是尊重自己。to respect others is to be respected  

 做奴隶就等于放弃自由。to become a slave is to give up one's freedom  

不定式作表语可以说明主语的具体内容或表示目的。

 他的愿望是成为一名宇航员。His wish is to become an astronaut  

 他希望能被大学录取。What he hoped was to be admitted into the university  

 活着就是要做一些有价值的事情。to live is to do something worthwhile  

有些作表语的不定式，在结构上是主动的，但在意义上却是被动的。

 她应该受到责备。She is to blame  

 此房出租。The house is to let  

 结果不久就会看到。The result is not long to see