看来我前面文章《不定式的初步理解》的朋友肯定知道，动词不定式是指不受人称、数量和时态等条件限定的动词形式。它很多时候会省略介词to，直接使用后面的动词原形。那到底哪些情况下会省略to呢？我们来仔细了解一下。
1、在使役动词后面
使役动词是指让别人做事情的动词。主要有have、get、make、let、leave、help等。
I would have Tom do this job.
You shouldn’t have let him leave without a word.
2、在感官动词后面
I saw Tom fall off his bicycle yesterday afternoon.
3、当两个或以上的不定式连在一起的时候，后面的to可以省略。但是当表示几个不定时之间比较或强调的时候则不能省略to。
I am goingto see the president and ask him to solve this problem.
Tom is here to make friends not to make trouble.
4、前有do，后无to
如果前面的主语有do，做表语的不定式省略to。
What I want to do this weekend is see my father.
5、except/but后面省略to
Tom had no choice but do his homework again.
I can do every thing except washing.
6、help后面可以省略to
help后面的to可以省略也可以保留。
Tom helped me do my homework.
注意，使役动词在主动格式时可以省略to，但是在被动的时候就需要加上to。
Tom made his mother repeat the story.
Tom’s mother was made to repeat the story.
