Need的用法
1. need 是英语中两个比较特殊的动词之一（另一个是dare），既是及物动词又是情态动词。作情态动词用多见于英国英语中，而且仅用在否定句和疑问句中。如：
require名词
情态助动词
及物动词
肯定
——
He needs to go.
否定
He needn’t go.
He doesn’t need to go.
疑问
Need he go?
Does he need to go?
2. need 作情态助动词通常不用在肯定句中（*He need go now.）, 但在表示怀疑或否定概念的主句之后的宾语分句里或主语分句里，可以用情态助动词的肯定形式。如：
I don’t think you/ he need go just yet.
I wonder if we need take sleeping-bags.
The only thing you need to do is (to) fill in this form.
(=You don’t need to do anything else。)
All you need do is to take a taxi from the airport.
情态动词need的肯定式主要用在正式文体中。在非正式文体中，need作及物动词用也许更普遍。如：
I wonder if we need to take sleeping-bags.
I don’t think he needs to go just yet.
The only thing you need to do is (to) fill in this form.
3. need 没有过去、现在的时态区别。如果要表示过去时间可用“need have + -ed分词”的结构。如：
Need you have told him about my plans?
You needn’t have told him about my plan.
据CGoEL, You need not have done it. 几乎等于You did not need to do it. 但是，need have+-ed 分词结构隐含有与事实相反的意思，need to 的结构则没有。如下一句中，我们就不能用need not have said 来代替 did not need to say:
Anne was too nervous to reply, but fortunately she did not need to say anything.
编者注：did not need to say anything 指Anne 并没有说任何的话。如果改为need not have said则指Anne 说了话，但是不必要。
据PEU，needn’t have + -ed分词与didn’t need to的意思不一样（这与CGoEL的说法有些不一样）。试比较：
She needn’t have hurried. (It wasn’t necessary to hurry, but she did.)
She didn’t need to hurry. (It wasn’t necessary to hurry; we don’t know whether she did.)
I needn’t have gone to the station. (I made an unnecessary journey.)
I didn’t need to go to the station. (It was unnecessary to go—I don’t say whether I went or n
ot, but I probably didn’t.)
DCE持与PEU同样的观点：He needn’t have gone.这句话表示他去过了，但He didn’t need to go. 这句话，我们不清楚他是否去过。
4. needn’t 在间接引语里可以保持不变，或由didn’t / wouldn’t have to来代替。如：
“You needn’t come in tomorrow,” he said.
→He said I needn’t / didn’t have to come in the next day.
5. 回答need 的疑问句，可用下面形式：
--Need they leave now? (BrE) / Do they need/ have to leave now?
--Yes, they must/ have to/ need to.
--No, they needn’t.
回答Need you have hurried / written, etc? 的疑问句可用下面形式：
Yes, I had to. / No, I needn’t have.
6. need 用作名词时，常带介词of 或for. 据EPI，只有need在意思上跟它用做完全动词的动宾部分相一致时，才能用(have) need of，即： to need sth. →to have need of sth.。 如：
We have no need of your advice.
He had need of five hundred Francs.
I have no need of doctors.
当need指“迫不得已的情况”(compelling circumstances) 或在意思上与助动词need相应的时候，用need for（多用于there be结构）表示。
如：There is no need for panic.
(比较：You needn’t get panicked.)
Is there any need for all this hurry?
(比较：Need there be all this hurry?)
There’s a great need for a book on this subject.
有时need of 和need for 之间区别甚微，如：
There is a need of/ for more science teachers.
Ann’s need of/ for money was becoming acute.
在这种情况下，of指需要的性质，for 指应满足需要的东西。
但是在某些句子当中，need of 可能产生歧义，如The need of nurses is well known.就有两种理解：Are the nurses needy or are they in short supply? 改为下面的说法就很清楚：Nurses’ low pay is well known. 或The shortage of nurses is well know.
7. if need be 是固定虚拟语气的短语，只指现在或将来，相当于if (it is) necessary. 如：
If need be we can always bring another car.
I’ll ask someone to help you, if need be.
8. （某人）没有必要做某事可用There’s no need (for sb.) to do sth. 或It is not necessary (for sb.) to do sth. 或 It is not necessary +that- 分句表示，没有It is no need (for sb.) to do sth.的结构。如：
There’s no need to tell the police about the accident.
It’s not necessary to tell the police about the accident.

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