need的用法讲解.doc

情态动词need的用法讲解
（1）表示 "必要;必须"，通常用于否定句和疑问句
Need he work so hard? 他需要这么用功吗？
You needn't worry about it. 你不必为此担忧。
I hardly need say how much we missed you. 不必说我们多么的想念你。
（2）在肯定句中，它被must或have to 取代。
—Need I come? —我需要来吗？
—Yes, you must/have to.—需要。
You needn't see him, but I must /have to.你不必去看他，但我必须去。
（3）“need+一般式”，通常表现在和未来，有时也可指过去。
She need not come. 她不必来。（现在或将来）
We were told that we needn't do that.我们被告知不必做那事。（过去）
Need she go yesterday?她需要昨天走吗？（过去）
如果从上下代看不出具体时间时，通常不用情态动词need表过去，而用实义动词need的过去时或had to表示。
She didn't need to come.
She didn't have to come
She had not to come.她不必来。
（4）“need+完成时”表示过去不必做而实际做了的事。
You needn't have hurried.你本不必这么匆忙。
Peter needn't have done it yesterday.彼得昨天本不必做这件事