F．分裂不定式
动词不定式to do通常是不拆开的，但偶尔也可在不定式符号to和动词原形之间插入一个副词，构成分裂不定式。 He was too ill to completely carry out that program. 他病得太重，不能完成那个项目。 He has made up his mind to once more try this method. 他已经下定决心再试试这个方法。
G．用作独立成分的不定式 有一些不定式短语可以作状语修饰整个句子，也可被称为插入语。 To be honest, we are not sure to find the girl in the forest. 说老实话，我们不能确保在森林里能找到那个女孩。 To be frank, I don't agree with what you said. 坦率地说，我不同意你说的话。
必背：用作独立成分的不定式 to tell you the truth 说老实话 to be frank 坦率地说 to begin with 首先 to be brief 简言之 to make a long story short 长话短说 to be exact 精确地说 to say nothing of 姑且不说 to conclude 总而言之 to be sure 诚然，固然 to do him justice 说句对他公道的话 so to speak 可以这么说 H．用主动式表示被动含义的不定式 动词不定式在句中究竟用主动还是被动，有时比较复杂，主要有下面几种情况：
1．不定式做后置定语，和被修饰的名词或代词构成逻辑上的动宾关系，但又和该句主语构成逻辑上的主谓关系时。 Do you have anything to say on this question 针对这个问题你有什么要说的吗？ He is a pleasant person to work with. 他是一个与其合作起来令人感到愉快的人。
2．不定式作形容词的宾语，和句子主语构成逻辑上的动宾关系时。 The book is difficult to understand. 这本书很难理解。 The chair is comfortable to sit on. 这把椅子坐起来很舒服。
3．There be结构中，当说话人考虑必须有人去完成某件事时。 There is nothing to worry about. 没什么可担心的。 There is nothing to fear. 没有什么可害怕的。 比较： There is a lot of work to do. 有许多事情要做。（表示某人必须做这工作） There is a lot of work to be done. 有许多事情要做。（强调有许多事情必须做） She has two letters to type. 她有两封信要打。（自己打） She has two letters to be typed. 她有两封信要打。（别人打） I．表示虚拟语气的不定式完成式。 I hoped to have met him at the railway station, but he didn't turn up. 我本希望在火车站接到他，但他未露面。 We would love to have gone to the match, but the tickets were all sold out. 我们原想去看这场比赛的，但票已售完了。 The plane was to have taken off at 9, but something went wrong. 飞机原计划九点起飞，但出现了一些故障。
J．用于感叹句。 不定式可用于感叹句，含有惊异、不满、惋惜或赞美等感情色彩。 To think that he should do this! 想想，他竟然干出这等事！（表示惊讶） Oh, God, to see her dance ! 哦，天哪，看看她的舞蹈！（表示赞美） To think that all the money has been wasted. 想想，所有的钱都被浪费掉了！（表示不满）
四、 关于不定式符号的几个问题
A．不带to的不定式 1．在口语中，动词原形come和 go后可接不带to的不定式。 Go tell her. 去告诉她吧。 Come have a glass. 来喝一杯。 2．在why引起的一些问句中，疑问词直接跟动词原形或not+动词原形。 Why make so much noise 为什么发出这么大的噪音？ Why not join us 为什么不加入我们？
3．在had better, had best, would rather, would rather...than, would sooner, would sooner...than, cannot but, cannot choose but, cannot help but等结构后直接跟动词原形或not +动词原形。 You'd better listen to your teacher's opinion. 你最好听一听老师的意见。 We had best call for the doctor at once. 我们最好马上就请医生来。 She can't do anything but ask silly questions. 她一直在问一些愚蠢的问题。 Rather than ride on a crowded bus, he always prefers to ride a bicycle. 他宁愿骑自行车，也不愿挤公共汽车。 He cannot but move to another street, because his building has to be pulled down soon. 他不得不搬到另一条街上去，因为他住的大楼很快就要被推倒。 We cannot help but admire his courage. 我们情不自禁地钦佩他的勇气。
4．如不定式前有行为动词do，那么在表语从句中的不定式和介词except或but之后的不定式可不带to。 The only thing I could do was go home. 我能做的唯一一件事就是回家。 They could do nothing but wait for the doctor to come. 他们只能等待医生的到来。
5．在两个动词不定式并列使用时，为了避免重复，后面的不定式符号to可省略。 The little girl hardly knew whether to laugh or cry. 这小姑娘不知道是哭好还是笑好。 Can you help me to call him and ask him to attend the meeting at 200 p.m. 你能不能帮我打电话给他，叫他下午两点来开会？
6．在help之后，既可用带to的不定式也可用不带to的不定式。 Can I help (to) carry the box for you 我帮你搬箱子，好吗？
7．在一些固定搭配中用不带to的不定式。 He let go the rope. 他松开了绳子。 I hear say there will be an earthquake soon. 我听说不久就要有一次地震。 She made believe she was innocent. 她假装清白。8．在感官动词see, hear, watch, feel, notice以及使役动词make, let, have等后作宾语补足语的动词不定式不带to。 She watched the children cross the street. 她看着孩子们穿过了马路。 They made the boy apologize to his friend for being so rude. 他们让那男孩因他的粗鲁而向他的朋友道歉。 Don't forget to have him come earlier. 别忘了让他早点儿来。
B．不定式符号的单独使用 为了避免重复上文中出现过的动词，可以用不定式符号to来代替上文中出现过的不定式结构。 1．在助动词或情态动词之后，如be going to, used to, have to, ought to, be able to, be about to等。 She must go but you don't have to. 她必须走，但你没有必要。 ---Do you think I ought to go to see my doctor 你认为我应该去看医生吗？ ---Yes, I think you ought to. 是的，我想你应该去。 2．在want, decide, like, love, hope, wish, mean, refuse, try等动词之后。 You may go with them if you hope to. 如果你希望的话，你可以和他们一起去。 ---Did you go to see the Great Wall 你游览长城了吗？ ---I wanted to, but I was too busy. 我本来想去的，但我太忙了。 3．在做宾语补足语的ask, tell, order, advise, persuade, warn, wish, permit, allow, forbid等动词之后。 Don't do anything unless your father tells you to. 除非你父亲叫你去做，不然不要做任何事情。 ---May I use your car 我可以用你的汽车吗？ ---No, I forbid you to. 不，我禁止你使用。 4．在对话的答语中的happy, glad, eager, anxious, willing, ready, pleased, afraid等形容词之后。 ---Will you lend me a hand 你能帮我一个忙吗？ ---I'm willing to, but I can't now. 我很愿意，但现在不行。 ---Would you please come to my birthday party tomorrow 明天下午来参加我的生日聚会好吗？ ---I'll be glad to. 我很乐意。 提示： 如果动词不定式是to be或to have，则一般不省。 --- Did you finish the work 你的工作完成了吗？ --- No, but I hoped to have. 没有，但我希望已经完成了。C．介词to和不定式符号to to既可以是不定式符号，后接动词原形；to也可以是介词，后接名词或动词的-ing形式。英语中有很多常用短语带有to，我们要正确判断to是不定式符号还是介词，千万不可混淆。
1． 不定式符号to He made it a rule to read English aloud for half an hour every morning. 他坚持每天早晨朗读半小时英语。 These young lads are longing to go to watch the football match. 这几个小伙子极想去看足球赛。 必背：常见的带不定式符号to的短语 be supposed to do应该做某事 be determined to do 决心要做某事 fail to do 未能做某事 go all out to do 全力以赴做某事 have the nerve to do 有胆量做某事 have a great mind to do 很想做某事 make a point to do 坚持做某事 make up one's mind to do 决定做某事 take the trouble to do 不辞辛苦地做某事 prepare oneself to do 有思想准备做某事
2． 介词to If you stick to the truth, you will have nothing to fear. 如果你坚持真理，就没有什么可害怕的。 You must get used to getting up early. 你必须习惯早起。 Isn't it time you got down to marking those papers 难道还没到你定下心来阅卷的时间吗？
必背：常见的带介词to的短语 be used to 习惯 be equal to 胜任 be given to 沉溺于 be opposed to 反对 be related to与……有关 devote oneself to 献身于 get down to 着手做 give rise to 引起 lead to 导致 look forward to 盼望 object to 反对 pay attention to 注意 put one's mind to 全神贯注于 stick to 坚持