非谓语动词之动词不定式(todo)的用法

非谓语动词之动词不定式（to do）的用法

非谓语动词是指在句子中不是谓语的动词，主要形式有：不定式、动名词和分词（现在分词和过去分词）。

“to do”动词不定式的变形

动词不定式的用法

充当主语（一般会用it 当形式主语）

To swim here is dangerous. =

It is dangerous to swim here.

To pass this English exam is unlikely. =

充当表语（多数情况下，可以转换成动词不定式做主语）

My job is to help with your English learning.

To help with your English learning is my job.

充当宾语（只能做某些动词的宾语，一般不做介词的宾语；有时用“it”做形式宾语）

I decided to attend this meeting last night.

I find it necessary to learn a foreign language.

注意：当以下动词欲接动词作宾语时，只能跟不定式作宾语。

decide, determine, learn, wish, hope

agree, plan, pretend, dare, refuse, fail

prepare, try, manage, help, promise

offer, beg, demand, afford, arrange, be supposed

充当宾语补足语

I persuaded him to make a speech in public.

注意：在感官动词／使役动词／help后（see, hear, watch, notice, make, have, let后不定式做宾补时，可省略“to”）

I saw them have a disagreement on who should sweep the floor. （我看到了他们争论的整个过程）

但，感官动词后面也可接Ving形式，表示正在进行。

I saw them arguing about who should sweep the floor. （我看到他们正在争论谁该扫地，并不一定看到了整个过程）

充当状语（目的，原因，结果状语，其逻辑主语与句子主语一致）

I wrote him a letter to further explain this matter. （目的状语）

I’m sorry to bother you.（原因状语）

He queued for hours at the box office only to find that the show was sold out. （结果状语，only + to find/realize/discover表示出乎意料的结果）

充当定语（不定式作定语，要放在所修饰的词的后面）

I have a lot of dishes to wash.

Do you have anything to say

There are 3 questions to answer.

一些固定句型中不定式省略“to”

had better

would rather do… than do…

why not do

“except/but” 有“do” 无“to”，有”to”无“do”

have nothing to do but do…

do everything but/except

have no choice but to

want nothing but/except to

当两个或多个作用相同的不定式并列（and/or/than）时，通常只保留第一个不定式的“to”.

He told me to stay there and wait for him.

It’s easier to persuade people than force them.

To try and fail is better than not to try at all. （否定式中“to”不能省略）

习题：

1. It’s great ________ (hear) this news that China team won the match.

2. He pretended ________ (sleep) when his younger brother came in.

3. We agreed ________ (meet) here but so far she has not turned up yet.

4. Although regular exercise is very important, it’s never a good idea ________ (exercise) too close to bedtime.

5. It’s going to rain. You’d better ________ (bring) the umbrella with you when going out.

6. You don’t have to run fast for long _______ (see) the benefit.