“may(might)+动词的完成式”表示“对过去发生的行为的推测”。

　　may have done 表推测时，隐含“不确定”。

　　might have done 表推测时，隐含的“不确定性”比“may have done”更深。

　　He may not have finished the work.

　　他可能还没有完成那项工作。

　　They may not have known it beforehand.

　　他们事先可能不知道这事儿。

　　You might have read about it in the papers.

　　你可能在报上已经看过这个消息了。

　　-Whatever has happened to George?

　　-I don't know. He may have got lost.

　　乔治发生了什么事?

　　我不知道,他可能迷路了。

　　might 表示的可能性比may小,语气较委婉。例如:

　　How quickly time passed! It might have happened yesterday.

　　时间过得好快啊!这事好像就发生在昨天。

　　He might have seen the surprise in my face.

　　他或许已经看到了我惊异的表情。