一、用作情态动词
1. 通常用在疑问句、否定句中，或与条件句whether, hardly, nobody等连用。
need+do，否定needn't +do
Need he go so soon? 他这么快就要走吗?
He needn't go．他不必走。
If she wants anything, she need only ask．若她想要什么，只需说一声就行。
2. need引导的疑问句，肯定回答要用must。
—Need I hand it in right now? 我需要现在就交吗?
—Yes, you must．是的，需要现在交。
—No, you needn't．不，不需要现在交。
3. need have done 的否定式或疑问式，表示“本来不必做某事，但事实上却做了”。
You needn't have helped me because I could make it.
你本没必要帮我的，我自己可以做到。
二、用作实义动词
1. 可用于疑问句、否定句和肯定句。
need +to do否定 don't/ doesn't need +to do
Does he need to go so soon? 他这么快就要走吗?
He doesn't need to go．他不必走。
2. need +名词
They need our help. 他们需要我们的帮助。
3. need doing表示被动含义。
The clothes need washing.这些衣服该洗了。
= The clothes need to be washed.
三、用作名词
All our need is just water. 我们所有人都需要水。
We are in need of a good rest. 我们需要好好休息。
There is no need for us to have a rest. 我们没必要休息。
A friend in need is a friend indeed. 患难见真情。
