以下几个英语单词有何区别？

might 和 may 没有本质上的区别，
一般情况下都可以交换使用。
但是，只能用 might 表达不真实的事件。
But we use only might （not may）when the situation is no real：

eg. If I knew them better，I might invite them to dinner.
(The stiuation here is not real because I don not knoe them
very well ,so I am not going to intive them.May is not possible in this example.)
以上是国外语法教科书上引用的。

maybe是副词,相当于perhaps,不能作谓语,may和 might都是情态动词(might是may的过去式),后面要加动词原形在一起构成谓语.
如:Maybe he is at home.= He may be at home.=Perhaps he is at home.

might是may 的过去式形式，长表示一种比may委婉，客气的语气，在句子中和其它动词一起构成谓语。如;It might rain today。
maybe 是副词"可能，大概 ，或许“，在句子中作状语，常置句首。如：Maybe it is going to rain today .大概要下雨了。