情态动词与形态动词？

情态动词 (Model Verbs) 又称为情态助动词 (Model Auxil-iaries)。英语中助动词主要有两类：一是基本助动词，如have, do, be；二是情态助动词，如may, must, need等。情态动词与其他动词连用表示说话人的语气。情态动词可表达建议、要求、可能和意愿等。情态动词没有人称和数的变化。在大学英语四、六级考试中，情态动词部分重点测试以下内容：

（1）情态动词+行为动词完成式

（2）情态动词+行为动词进行式

（3）情态动词+行为动词完成进行式

（4）某些情态动词的特殊用法

一、情态动词+行为动词完成式

情态动词+行为动词完成式即“情态动词+ have + v-ed分词”，表示对过去行为或动作进行推测、评论或判断。

1. must have v-ed

must have v-ed 表示推测过去某事“一定”发生了。其否定形式为：can’t / couldn’t have v-ed, 表示过去不可能发生某事。例如：

1）Since the ditch is full of water, it must have rained last night.

2）You couldn’t have met my grandmother. She died before you were born.

2. could have v-ed

could have v-ed 表示推测过去某动作“很可能”发生了。例如：

1）“The dictionary has disappeared. Who could have taken it?”

2）“Tom could have taken it. He was alone yesterday.”

3.may / might have