1.needn't 是当need 作情态动词时的否定形式,2.当你用Must提问时,可以用needn't 作否定回答3.当用于一般时,don't need 可以和needn't 互相转换然而过去时,需要用didn't need 代替 needn;t最主要的差别 ：don't need ...
needn't和don't need
1.needn't 是当need 作情态动词时的否定形式,2.当你用Must提问时,可以用needn't 作否定回答3.当用于一般时,don't need 可以和needn't 互相转换然而过去时,需要用didn't need 代替 needn;t最主要的差别 ：don't need ...