may和might的区别

may,might
1) 表示请求和允许.might比 may语气更委婉,而不是过去式.否定回答时可用can’t
或mustn’t,表示“不可以,禁止”.
----Might/ May I smoke in this room?
---- No,you mustn’t.
---- May/Might I take this book out of the room?
---- Yes,you can.(No,you can’t / mustn’t.)
用May I...征徇对方许可时比较正式和客气,而用Can I...在口语中更常见.
2）用于祈使句,表示祝愿.
May you succeed!
3) 表示推测、可能性（不用于疑问句）.
might不是过去式,它所表示的可能性比may小.
1．He may /might be very busy now.
2．Your mother may /might not know the truth.
三、 must
1) 表示必须、必要.
You must come in time.
在回答引出的问句时,如果是否定的,不能用mustn’t（禁止,不准）,而用needn’t,don’t have to（不必）.
---- Must we hand in our exercise books today?
---- Yes,you must.
---- No,you don’t have to / you needn’t.
2) must是说话人的主观看法,而have to则强调客观需要.Must只有一般现在时,have to 有更多的时态形式.
1． he play isn’t interesting,I really must go now.
2． I had to work when I was your age.
3) 表示推测、可能性（只用于肯定的陈述句）
1． You’re Tom’s good friend,so you must know what he likes best.
2． Your mother must be waiting for you now.