(一、在感官动词和使役动词后作宾补的不定式要省去to.常见的感官动词有feel、hear、see、notice、listen(to)、look at、smell、observe、watch(注视、观看)、overhear(偷听)、perceive(观察)等.常见的使役动词有have、let、make.例如:He listened to me repeat what Mr.Smith had said the day before.他听我重复史密斯在前一天说的话.二、在help后面作宾补的不定式,可以带to也可以不带to.例如:She helped the old woman (to) cross the street.她帮助老太太过马路.三、不定式(短语)作介词except、but、save、than的宾语,如果介词前面有实义动词do,后面的不定式不带to;反之,后面的不定式则带to.例如:We didn't do anything but stay at home watching TV for 3 hours.除了呆在家里看了3个小时电视外,我们什么也没做.He had no alternative but to go to see him.他除了去看他以外,别无办法.四、不定式作表语时to省略的几种情况:1.当句子主语是被动词do作谓语的定语从句修饰的all、all that、anything、the only thing(way),或thing前面有序数词(first、second)或last等修饰,或者是形容词最高级修饰时,to可以省略.例如:All you have to do is put it in the toaster and wait till it pops up.你要做的只是把面包片往烤炉里一放,便可等它跳起来.2.当句子主语是被不定式修饰的thing时,其表语的不定式符号to也可以省略.例如:The thing for you to do is face the facts.你要做的事情是面对事实.3.当主语all被以动词say作谓语的定语从句修饰时,其表语的不定式符号to也可以省略.例如:All they said is hurry up.他们只是说赶快.4.what引导的主语从句中含有实义动词do时,其后表语的不定式符号to也可以省略.例如:What I really wanted to do was drive all night.当时我真正想要做的是开一整夜的车.五、请记住下列动词+动词结构:make say/ tell(听说)、make believe(假装)、make do(将就,凑合)、let slip(使溜走,无意中泄漏)、let fly(飞掷)、let fall(说出,吐出)、let drive(朝……打了一下)、let drop(说出).例如:I don't know how she makes do on so small an income.我不知她如何靠如此少的收入将就着生活.六、当不定式用于实义动词do+比较级/less/else/other等词+than后面时,一般不带有to,如是其他动词则要求带to.例如:In the course of a day,students do far more than just attend classes.在一天
