什么情况下用动词不定式？有什么巧记的规律吗？

Question

英语的动词不定式在什么情况下使用？怎样巧妙的分出该不该用动词不定式？

Answer 1

一、动词不定式在句子中不能充当谓语，没有人称和数的变化。

二、动词不定式是由“to+动词原形”构成(有时可以不带to)。动词不定式的否定形式是“not+动词不定式”(not不与助动词连用)。

三、动词不定式短语具有名词、形容词和副词等的功能，可在句中用做多种句子成分。

1、主语：常置于句末，而用it代替其做形式主语。
例：To go in for sports helps you stay fit.(book4 L28)
It helps you stay fit to go in for sports.
It is dangerous to swim in the deep sea on your own.

注：此句式中不定式逻辑上的主语可由for或of引出，逻辑主语由of引出时，表语的形容词为kind，nice，good，polite，clever，foolish，right，wrong等表示

评价的形容词。例：It's right for him to refuse the invitation.(him为逻辑主语)

2、表语：Our duty is to protect the environment.

3、动词宾语：此种情况可按固定搭配或句式去记。
例：Would you like to see my photos?
Kevin planned to visit his uncle.(book4，L11)

和plan用法一样的词还有：start，want，agree，hope，begin，decide等。
I found it very difficult to get a job.(it为形式宾语)

4、宾语补足语：(1)在多数复合宾语及物动词后要带to：
例：I asked a friend to read it to me.(book4，L2)
(2)在表示感觉、致使等意义的动词
(see，watch，hear，feel，notice，observe，make，let，have，help等)后不带to。
例：They heard him sing a pop song in the meeting room.

5、定语：动词不定式做定语放在所修饰的名词的后面。

例：Vinny is the first disabled person to sail around the world.(book4，L1)

6、形容词补足语：在表示心理、感情、评价等的形容词后，对其进行补充说明。

例：We are very glad to meet you again.

7、状语：表示目的、原因、程度等。

例：They brought in photos of their families for me to look at.(book4，L2)

8、“疑问词＋不定式”用法：不定式前可带what，who，which，where，when，how等疑问词，这种不定式短语在句中多用做宾语。

例：He didn't tell me where to go.
9、在初中阶段还涉及到“不定式被动语态一般式(to be+过去分词)”

例：There are twenty more trees to be planted.

1 不定式作宾语

1) 动词+ 不定式
afford aim appear agree arrange ask be decide bother care choose come dare demand desire determine expect elect endeavour hope fail happen help hesitate learn long mean manage offer ought plan prepare pretend promise refuse seem tend wait wish undertake
举例：
The driver failed to see the other car in time.
司机没能及时看见另一辆车。
I happen to know the answer to your question.
我碰巧知道你那道问题的答案。

2）动词+不定式 ； 动词+宾语+不定式
ask, beg, choose, expect , hate, help intend like, love, need prefer, prepare, promise, want, wish…
I like to keep everything tidy. 我喜欢每件东西都保持整洁。
I like you to keep everything tidy. 我喜欢你年使每件东西都保持整洁。
I want to speak to Tom. 我想和汤姆谈话。
I want you to speak to Tom. 我想让你和汤姆谈话。

3） 动词+疑问词+ to
decide, know, consider forget, learn, remember, show, understand, see, wonder, hear, find out, explain, tell
Please show us how to do that. 请演示给我们如何去做。
There are so many kinds of tape-recorders on sale that I can't make up my mind which to buy.有这么多的录音机，我都拿不定主意买哪一种。

注意:疑问词带不定式在句中作成分时，谓语动词用单数。
The question is how to put it into practice.
问题是怎样把它付诸实施。

参考资料：http://www.windsn.com/main/grammar/0700.htm

Answer 2

做定语 状语 还有就是固定词组中包括不定式