由于动词不定式与其修饰的词之间往往有动宾关系，如果该不定式是不及物动词，其后应有必要的介词。
她有一个孩子要照看。She has a child to take care of
没什么可担心的。There is nothing to worry about
他没有可依靠的朋友。He has no friend to depend on
今天上午我有许多事情要处理。I've got a lot of things to see to this morning
他没有遵守诺言定期给他父母亲写信。He broke his promise to write to his parents regularly
我们学生应该有勇气面对任何困难。We students should have the courage to face any difficulty
我不想和你吵架。I have no wish to quarrel with you
现在是上课的时间了。Now it is time to begin our class
我需要一个地方打个盹。I need somewhere to take a nap
那就是打开罐头的方法吗？is that the way to open the can?
不定式作状语可以表示行为的目的、结果、原因、条件等。
我在存钱买电脑。I'm saving up to buy a computer
为了救那个孩子，他献出了生命。to save the child he laid down his life
有时为了强调或突出这种目的，也可以用 in order to do， in order not to do, 和 so as not to do，so as to do 结构。 so as to do 不可以置于句首。
免得浪费了你的时间so as not to waste your time
以免伤害到它们。so as not to harm them
人洗澡是为了清洁。One baths so as to get clean
为了占到好座位，我们早早就去了。We went early so as to get good seats
为了吸引注意，他又嚷嚷又挥手。He shouted and waved in order to be noticed
我要把他的电话号码记下来，以防忘记。I'll write down his telephone number so as not to forget it
他赶到车站，发现火车已经开走了。He got to the station only to find the train had gone
我说了什么话使你气成这样？What have I said to make you so angry?
散会后，他们分手了，从此再也没有见面。After the meeting they parted never to see each other again
如此 以致 so as to do
把你的自行车借给我好吗？Would you be so kind as to lend me your bicycle？
如此 以致such as to do
我们还没蠢到竟会相信他。We are not such fools as to believe him
足以 ;足够 去做某事 enough to do
他跑得不够快 没赶上火车。He didn't run fast enough to catch the train
仅仅为了 ; 结果却only to do
他搬起石头砸自己的脚。He lifted a rock only to drop it on his own feet
太 而不能 。too to do
她的视力太差了，不能看这么小的字。His eyesight is too poor to read such small letters
注意： too to 结构中的形容词如果是 渴望，eager高兴， pleased 快乐，happy 准备好，ready，动词不定式不表示结果，也没有否定的意思。
那个男孩非常急切地想要得到一本地理书。The boy was too eager to get a geography book
他很急切地想知道考试结果。He is too anxious to know the examination results
我当时不听你的话，真是傻瓜。I was a fool not to listen to you at that time
看到他处于这么困难的情形，她哭了。She wept to find him in such a difficult situation
一个人如果看不到这点，那他就是瞎子。a man would be blind not to see that
这么晚才动身，你怎么能赶上火车？How can you catch the train to start so late?
如果不定式的逻辑主语不是句子的主语，此时一般用“ for +名词（代词）+不定式”来构成不定式的复合结构
这个箱子让这个小男孩来搬太重了。This box is too heavy for the little boy to carry
那个由你来决定。That's for you to decide
他站到一边让我通过。He stood aside for me to pass
我有几本书送给你读。I have some books for you to read
be +不定式结构可以表示将来发生的动作，
表示命令和指示
这房间要上锁。The room is to be locked
你不能站在这里。You are not to stand here
表示计划或安排
我们安排下一个月开始这项工作。We are to begin the work next month
下一步该怎么办？What's to be done next?
疑问词+不定式结构
疑问词 who, what, which, when, where, how, why, 后加动词不定式构成不定式短语，它在句中可作主语、宾语和表语。
我不知道要不要去开会。I don't know whether to go to the meeting or not
问题是如何处理乘客们丢弃的垃圾。The problem was how to get rid of the waste thrown by the passengers
何时参观故宫博物院还没有决定。 When to visit the Palace Museum has not been decided yet?