英语 need何时情态动词 何时实意动词

在肯定句中，如果随时态的变化而变化，那就是实意动词，在否定句中，如果用don't，就是实意动词，如果直接加not，就是情态动词

当need后面有to的时候肯定是使役动词。

Need的用法
Need有两种用法,可以用做特殊动词,或者用做普通动词,二者不可兼用.
特殊动词need只用于疑问句和否定句,用来表示有必要吗或没必要.肯定式是must.
不能接名词,只能和普通动词不定式5构成合成谓语,无人称和时间变化.
Need you go there now ?
Yes, I must . No, I needn’t.
普通动词need不能提前疑问也不能加not否定,含义是需要.疑问和否定要借助于特殊动词do. 可以接名词做宾语.也可以跟4to do(=have to do) ,6doing 做宾语.有时间和人称变化.跟6做宾语时,其主语往往是物,主动形式表被动结构.
I need to use the bathroom.
Do you need to have a book ?
Yes, I do . No, I don’t need to have a book.
I need a book.
Do you need a book ?
Yes, I need a book. No, I don’t need a book.
She needs your help.
Does she need your help ?
Yes, she does. No, she doesn’t.
He needed to take a taxi,or he would be late.
Did he need to take a taxi ?
Yes, he did. No,he didn’t.
Your shoe needs mending .
Does your shoe need mending ?
Yes, it does. No,it doesn’t.

A. 实义动词：
1、陈述句：I need two more people.
2、疑问句：Do you need more people?
3、否定句：I don't need so many people.
4、句型：need + to do
-I need to go at once.
-Do I need to go at once?
B. 助动词：
1、否定句： You needn't come with me.
He needn't eat it if he doesn't like it.
2、老式用法：
Need I come with the tool?
C. 鉴别实义动词以及助动词用法：
1、陈述句：Ineed to go at once.
如果need后面有to do，那么它就是实义动词。
因为助动词后面永远跟原形动词，比如，He should go at once.
而不是He should to go at once.
2、否定句：You needn't come with me.
这个need后面没有to come，所以，它是助动词。
同样一句话，把need当作实义动词来用，就成了：You don't need to come with me.