plan, prepare, pretend, promise, refuse, wish等动词后需接不定式作宾语。

The government decided to rebuild the damage bridge.

②decide, know, consider, forget, learn, remember, show, understand, see, wonder, hear, find out, explain, tell等动词后常接"疑问词+不定式"作宾语。

The driver wondered how to start the car in such a cold morning.

1. 不定式作表语

①不定式作表语一般表示具体动作，特别是表示将来的动作。

My wish is to join the army after graduation.

②如果主语是不定式，表示条件，表语也应用不定式，表示结果。

To see is to believe.

③如果主语的中心词是aim, duty, hope, idea, happiness, job, plan, problem, wish等，或是以wish引导的名词性从句，不定式作表语对其作补充说明。

His job is to feed animals.

2. 不定式作宾语补足语：

①英语中advise, allow, ask, beg, encourage, expect, force, forbid, get, order, permit, persuade, require, teach, tell, want, wish, warn等动词后常接不定式作宾语补足语，且不定式符号to不能省略。

She asked me to accompany her to the airport.

②不定式在动词let, make, feel, hear, see, observe等后作宾语补足语时，不定式符号to需省略。

The accident made us realize that safety can't be ignored.

③动词help接动词不定式作宾语不足语时，不定式符号to可省略也可不省略。

After the dinner he helped his mother (to) wash up the dishes.

3. 不定式作定语：

不定式作定语，一般都是作后置定语，修饰前面的名词或代词。

①主谓关系，被修饰的名词或代词实际上是不定式的逻辑主语。

We need some people to help pick apples.

②动宾关系，被修饰的名词或代词是动词不定式的逻辑宾语。

I have many things to do.

同位关系，不定式是对其所修饰的名词作解释说明。

We've made a plan to spend the weekend.

4. 不定式作状语：

不定式作状语，可表示动作的目的，结果，原因，条件和方式。

①to do, in order to do, so as to do都可表示目的，但to do, in order to do的位置既可在句首，又可在句末；而so as to do只能放在句末。

I left home at seven so as to/in order to be there on time.

②表结果，不定式在下列结构中表示谓语动作的结果，不定时的动作一般在句子末尾。

⑴表示终结性的动词find, see, hear, learn, discover的不定式，常表示出乎意料的结果，并且不定式前常有never, only等副词修饰。