不定式 不定式的构成非常简单是to+动词原形。当然to有时也可以不带。动词不定式没有人称和数的变化，可以担当除谓语外的任何句子成分。那什么时候可以不带to呢?
不定式省to有四种情况： 使役动词 let,have,make 等后接不定式。如：Let him go! 让他走! would rather，had better后。如：You had better stay at home.你最好呆在家里。 Why... / why not...后。如：Why not have a good rest on Sunday? 为什么星期天不好好休息一下呢? 感官动词 see, watch, look at, hear, listen to, smell,feel, find 等后作宾补，省to。如：I saw him dance. 我看见他跳舞。 注意：这些情况在被动句中可千万不可省to 如：The boss made them work the whole night. 变成被动句：They were made to work the whole night. 不定式的特殊用法： It与不定式：动词不定式可以做主语，但如果动词不定式太长，显得头重脚轻的，那么我们就可用形式主语it代替，而把真正主语(即不定式)放于句尾。 如: It is not difficult for me to study English well.(对我来说学好英语是可能的。)
不定式还可以充当句子的宾语，但有些动词，如find，think，believe 等，在语法上不能接受不定式作宾语，只有用it作形式宾语，从而把动词不定式置于句尾。这样的不定式可继续充当其宾语的作用。 如: I found it difficult to fall asleep.我发现很难入睡。 还有一点：动词不定式，还可用在how，when，where，what，which 等疑问代词或副词之后，与其共同作宾语。如：I don't know how to use a computer.我不知道怎样使用电脑。Remember?
too...to...和enough...to：too...to表达"太 ... 一致于不能..."。 enough ... to 表达 "足以..."。这两个词组的用法用两个例子就可以说清楚了。 The box is too heavy for me to lift.这个箱子太沉了，我提不动。 He is old enough to go to school.他到上学的年龄了。也就是说，他的年龄足够上学了。
练习： 1. Tell him ___ the window. A. to close not B. not to close C. to not close D. not close 2. Paul doesn't have to be made ___. He always works hard. A. learn B. to learn C. learned D. learning 3. You'd better _______the story in Japanese. A. say B. speak C. tell D. talk 4. The patient was warned ___ oily food after the operation. A. to eat not B. eating not C. not to eat D. not eating 5. ---- I usually go there by train. ---- Why not ___ by boat for a change? A. to try going B. trying to go C. to try and go D. try going 6. There are some books on the floor, would you like ________? A. to pick them up B. to pick up them C. pick it up D. pick up it 7. She is very ill, let's _______a doctor at once. A. to wake up B. send for C. to pay for D. pay for 8. I want ________a teacher when I grow up. A. to be B. to C. be D. being 9. It's cold here. You'd better ______ your coat. A. not take out B. not to take down C. not take off D. not to take away 10. My mother told me ________more water. A. drinking B. drank C. to drink D. drink
