may not/can't/couldn't/needn't/mustn't举例区别意思和用法

may not 语气较弱，”可以不”，You may not finish your homework;
can't ”不能”; You can't be too serious;问句回答时：Can I go out to play? No, you can't. 或做may问句的回答：May I sit here? No, you can't.;
couldn't 语气较委婉，”不能”,常做could疑问句的回答：Could I sit here? I'm afraide you couldn't;
needn't 表示不必这么做：常做must问句的回答：Must I finish my homework today? No, you needn't.
mustn't 语气强，”禁止”:You mustn't step on the grass.

我说说
1 表示可能,不确定的
2 有点生硬的 表示客观上的原因是之不能(注意5)
3 意思同上,但显得语气缓和
4 没必要.不必.
5 表示主观上的原因,使之不能
不好意思,只能说这些了,希望帮的上忙.

may not 语气较弱,”可以不”,You may not finish your homework;
can't ”不能”; You can't be too serious;问句回答时：Can I go out to play?No,you can't.或做may问句的回答：May I sit here?No,you can't.;
couldn't 语气较委婉,”不能”,常做could疑问句的回答：Could I sit here?I'm afraide you couldn't;
needn't 表示不必这么做：常做must问句的回答：Must I finish my homework today?No,you needn't.
mustn't 语气强,”禁止”:You mustn't step on the grass.