need在英语中用法有哪些
“need”既可以作情态动词，也可以作实义动词，扮演双重角色，但是它们的用法不同，比较复杂，是升学考试中出题人钟爱的一个考查点。
作为情态动词的“need”的用法与其他情态动词“can”，“may”，“must”的用法基本相同：没有非限定形式，即没有不定式、-ing分词或-ed分词等形式;第三人称单数现在时没有词形变化;下面是小编整理的一些关于need在英语中用法，欢迎大家阅读！
need在英语中用法有哪些?
一、NEED与句子类型
(本条可参照ANY的用法。)
NEED可用于：
1.否定句/含有否定意义的句子
1)否定句
含not/hardly/never/nobody等词语。
I needn’t say anything.
He need hardly advise me.
You never need tell me this or that.
Nobody need help me.
I don’t think he need come.(否定转移)
注：NEEDN’T的意思其实有三种，即不必要/不一定/不应该，视具体语境而定。
2)含有否定意义的句子
含only/but/all/before/than等词语。
He need only wait here.
You need but consider the matter to understand its importance.
That’s all that need be said.
Do not stay longer than you need.
There was another hour before I need go out into the cold.
2.疑问句/表示疑问的从句
1)疑问句(包括否定疑问句)
Need he say it again?
2)表示疑问的从句
I wonder whether/if I need see her.
3.条件句
含if/unless等词。
If he need come, he will.
本条要点简单概括起来就是，NEED不能用于肯定句。以下的各种用法也遵循这条规则。
二、NEED与时态
1.现在时
NEED常用于现在时。
You needn’t stay.
2.将来时
You needn’t have your blood pressure taken tomorrow.
3.过去时
NEED的过去式仍然是NEED。
1)过去时间由一过去时间状语表示
He need not come yesterday.
2)过去时间由另一过去时动词表示。
All he need do was to inquire.
It was clear that he need never trouble to get up at seven again.
I told him he needn’t be in a terrible fix.
注：表示过去的NEED常用于间接引语中。
(本条可参照must的用法)
三、NEED与虚拟语气
1)NEED用于虚拟条件句
(本条可参照虚拟条件句的构成及用法。)
If money were useless, we need not struggle for it.
If you had been careful enough, you need not have suffered.
注：本条用法较为少见。
2)NEED单独使用：NEEDN’T HAVE DONE
(本条可参照SHOULDN’T HAVE DONE的用法。)
You need not have worried.
注：NEED HAVE DONE的形式较为少见
Need you have scolded him so severely for his bad work? He had done his best.(否定意味)
He need have gone and sent that letter in person.(实际上没有做)
四、NEED与推测
NEEDN’T表示“不一定”。
(本条可参照must/can的用法。)
1)NEEDN’T+BE
It needn’t be hot in Florida now.
对比：
It can’t be hot in Florida now.(一定不)
It must be hot in Florida now.(一定)
2)NEEDN’T+HAVE DONE
He need not have seen much of the world, though he is an old man.
对比：
He can’t have seen much of the world, for he is just a little boy.
He must have seen much of the world, for he has been traveling so widely.
五、NEED与问句
1)反意疑问句的构成
You needn’t go, need you?
2)答句的构成
--- Need he go?
--- Yes, he must/has to/needs to.
--- No, he needn’t.
(本条可参照must的用法)
六、情态动词NEED与实义动词NEED
1)使用范围
作为实义动词的NEED有人称、数和时态的变化，使用范围更为广泛，不受句子类型和时态的限制。在肯定句、过去时和将来时的句子中，一般使用作为实义动词的NEED。
He needs to see a doctor straightaway.(此处needs to不能换做need，因为本句是肯定句)
Will he need to start earlier?
注：
NEED TO BE DONE与NEED DOING可以互换，后者更为常用(这里的NEED均为实义动词)。
2)含义差别
NEEDN’T HAVE DONE与DIDN’T NEED TO DO表示“不必要”的时候，在意义上有所差别，前者表示“本不必做……”，实际上已经做了(NEED为情态动词);后者单纯地表示“不必做……”(NEED为实义动词)。