不定词
不定词的构成
不定词是动词的原型。在英语中，当我们谈到不定词时，一般指的是现在式不定词，这是最常见的一种。然而还有其他四种型态不定词：完成式型态的不定词丶完成进行式型态的不定词丶进行式型态的不定词以及被动语态的不定词。
不定词又分为两种型态：
- 带 to 的不定词 = to + 动词原型
- 不带 to 的不定词（又称「零不定词」）= 动词原型
现在式不定词就是您在字典上会看到的动词型态。
| 带 to 的不定词 | 零不定词 |
|---|---|
| to sit | sit |
| to eat | eat |
| to have | have |
| to remember | remember |
否定型不定词则是在任何型态的不定词前加「not」即可。
举例
- I decided not to go to London.
- He asked me not to be late.
- I'd like you not to sing so loudly.
- I'd rather not eat meat.
- I might not come.
带 to 的不定词的作用
带 to 的不定词用于很多句构上，通常表达某事的意图，或者表达某人对某件事的看法。带有 to 的不定词可以接的动词类型有很多，这部分可以参考接不定词的动词。
带 to 的不定词表明某动作的意图或目的
在这种情况下，不定词的 to 意思就跟 in order to 或 so as to 一样。
举例
- She came to collect her pay cheque.
- The three bears went to find firewood.
- I am calling to ask you about dad.
- You sister has gone to finish her homework.
带 to 的不定词用作句中的主词
这是正式用法，多用于英语正式书写上，口语上较少见。
举例
- To be or not to be, that is the question.
- To know her is to love her.
- To visit the Grand Canyon is my life-long dream.
- To understand statistics, that is our aim.
带 to 的不定词表明某件事可以被用来做的事
在这种句型中，带 to 的不定词接着是名词或代名词。
举例
- The children need a garden to play in.
- I would like a sandwich to eat.
- I don't have anything to wear.
- Would you like something to drink?
带 to 的不定词接在形容词后
带 to 的不定词接在形容词后的句型很常见，这类语句的公式如下：
主词 + Be 动词 + 形容词 + (for/of 某人) + 带 to 的不定词 + (句子的其馀部分)
| 主词 | + Be 动词 | + 形容词 | (+ for/of 某人) | + 带 to 的不定词 | (+ 句子的其馀部分) |
|---|---|---|---|---|---|
| It | is | good | to talk. | ||
| It | is | good | of you | to talk | to me. |
| It | is | important | to be patient. | ||
| It | is | important | for Jake | to be patient | with his little brother. |
| I | am | happy | to be | here. | |
| The dog | is | naughty | to destroy | our couch. |
评论某事时用带 to 的不定词
在对某个名词评论时使用带有 to 的不定词，公式如下：
主词 + Be 动词 + 名词片语 + 带 to 的不定词
| 主词 | + Be 动词 | + 名词片语 | + 带 to 的不定词 |
|---|---|---|---|
| It | was | a stupid place | to park. |
| That | is | a dangerous way | to behave. |
| What you said | was | a rude thing | to say. |
| This | is | the right thing | to do. |
| Those | were | the wrong kind of eggs | to buy. |
| Jim | is | the best person | to hire. |
副词和带 to 的不定词一起使用
带 to 的不定词经常与副词 too 和 enough 一起用来表达满意或不满背后的原因。在句型上，too 和 enough 会被放在其修饰的形容词丶副词或名词的前面或后面，就如没使用带有 to 不定词的方式一样；接着在后面接带 to 不定词，表达数量或分量过多丶充足或不足的理由。通常带 to 不定词以及后面接的所有字词都可以移除，而剩馀的句子在文法上都还是正确的。
举例
- There's too much sugar to put in this bowl.
- I had too many books to carry.
- This soup is too hot to eat.
- She was too tired to work.
- He arrived too late to see the actors.
- I've had enough food to eat.
- She's old enough to make up her own mind.
- There isn't enough snow to ski on.
- You're not old enough to have grand-children!
带 to 不定词和疑问词一起使用
ask丶decide丶explain丶forget丶know丶show丶tell丶understand 等动词可以接在 where丶how丶what丶who丶when 等疑问词后，加带 to 不定词即可。
举例
- She asked me how to use the washing machine.
- Do you understand what to do?
- Tell me when to press the button.
- I've forgotten where to put this little screw.
- I'm not sure I know who to call.
零不定词（不带 to 的不定词）的作用
零不定词接在助动词后
举例
- She can't speak to you.
- He should give her some money.
- Shall I talk to him?
- Would you like a cup of coffee?
- I might stay another night in the hotel.
- They must leave before 10.00 a.m.
零不定词用在感知动词后
与感知动词一起使用，句型为动词 + 受词 + 零不定词。
举例
- He saw her fall from the cliff.
- We heard them close the door.
- They saw us walk toward the lake.
- She felt the spider crawl up her leg.
零不定词用在 make 和 let 等动词后
举例
- Her parents let her stay out late.
- Let's go to the cinema tonight.
- You made me come with you.
- Don't make me study that boring grammar book!
零不定词用在 had better 的措辞后
举例
- We had better take some warm clothing.
- She had better ask him not to come.
- We had better reserve a room in the hotel.
- You'd better give me your address.
- They had better work harder on their homework.
零不定词用在疑问词 why 后
在表达建议时，疑问词 why 后会接零不定词。
举例
- Why wait until tomorrow?
- Why not ask him now?
- Why leave before the end of the game?
- Why walk when we can go in the car?
- Why not buy a new bed?