need的用法（need to）

need作为情态动词（像can,must）的时候,后面加动词原形
例：
（1）肯定句 You need do that.
（2）否定句 You needn't do that.
(3)疑问句 Need I do that?
当need作为使役动词（行为动词）时，后面加名词或动词不定式加to do sth.
例：
（1）肯定句 I need your help.
(2) 否定句 I don't need your help
(3) 疑问句 Do you need my help？
（1）肯定句 I need to finish my homework.
（2）否定句 I don't need to finish my homework.
（3）疑问句 Do you need to finish your homework？

实义动词：need to do sth
情态动词：need do sth；但一定记住need 作情态动词时，一般只用于否定句与疑问句。

作一般动词,need to do sth, 否定为 don't need to do sth
作情态动词,need do sth, 否定为 needn't do sth