情态动词有一定的意义,但没有人称和数的变化,不能独立使用,它和后面的动词构成谓语. Zx xk 只作情态动词的 can/could, may/might, ought to, must 可情态可实义的 need, dare/dared 可情态可助动词的 shall/should, will/would 相当于情态动词的 have to, used to, had better, would rather