情态动词

A. 特征

特征 情态动词有一定词义，但不完全，不能单独作谓语，须和不带to的动词不定式（ought等除外）一起构成合成谓语；情态动词没有人称和数的变化；情态动词表示可能，能力，允诺，命令，愿望，敢于等情态。

B. 基本形式

原形 过去式 can could may might must must (or: had to) ought to ought to will would shall should need needed dare dared

C. 情态动词和否定词not连用时的简略形式

情态动词＋not 简略形式 例句 can not can't He can't ski.

他不会滑雪。 could not couldn't I couldn't speak English fluently then.

那时候我不能流利地讲英语。 must not mustn't You mustn't think only of yourselves.

你们不能只想自己。 should not shouldn't We shouldn't be so careless.

我们不应当这样粗心大意。 ought to oughtn't There oughtn't to be much noise in a library.

图书馆里不该喧闹。 will not won't I won't do so.

我不愿这样做。 would not wouldn't He wouldn't go to bed before he finished his homework.

他在完成作业以前不愿睡觉。 shall not shan't You shan't leave your post.

你不得离开岗位。 need not needn't You needn't go there alone.

你不必单独去那里。 dare not daren't She daren't swim in a river.

她不敢在江河游泳。

D. 情态动词的用法