May 的主要用法

一、may 作“可以”解，表示许可；否定式是 must not（“不准”）或 may not（“不可”）

1. May I use this instrument to measure? 我可以用这个仪器来测量吗？
2. They may wait to get online. 他们可以等待上网。
3. You must not do this experiment without reading carefully through (或 over) the instructions. 你没有仔细读完说明书，决不准你做这个实验。
4. You may not operate the multimedia computer like that. 你不可那样操作那台多媒体计算机。

二、may 作“或许”、“也许”解，表示可能性；否定式 may not 作“也许不”、“或许不”讲

1. A man's ability may be great or small. 一个人能力有大小。
2. They may succeed. 他们也许会成功。（表示将来时。也可用 Perhaps they will succeed 代之。由此可见，may 可用于现在时和将来时。）
3. It may be about three o’clock. 现在大概三点钟。
4. It may not take too much time to build two-bedroom economy houses. 建造两卧室经济房也许花费不了太多时间。
5. She may be buying an IC telephone card. 她也许在买一张 IC 卡（或电话磁卡）。

三、may 用于目的从句

1. He works and studies hard that (或 so that, 或 in order that) he may serve the people better. 为了更好地为人民服务，他刻苦学习和工作。
2. Cables are usually laid underground that their life may be prolonged. 电缆通常铺设在地下，为的是延长使用期限。

四、may 用于让步从句

1. We must fulfil our task, however difficult it may be. 无论我们的任务如何艰巨，我们一定要完成它。
2. No matter how hard a solid may be, we can change its shape. 不管一个固体如何坚硬，我们总能改变它的形状。
3. Whatever may happen, we are determined to do this work. 无论发生什么事情，我们下定决心去做这项工作。

五、may 用于条件句或假设句里

1. If he arrives here, he may come to help us. 如果他到达这里，他也许来帮助我们。（真实条件句）
2. If he should need this home computer, he may use。如果他万一需要这台家用计算机，他可以使用它。（假设句）

六、“may + have + 过去分词”表示现在对过去事物的推断

1. They may have tried every means. 他们那时也许试用了各种方法。（或译“……各种手段。”）
2. He may not have cut that steel plate into halves. 他（当时）也许没有把那块钢板对开切割。
3. She may have arrived already. 那时她可能已经到了。
4. He may have been visiting these factories. 他那时可能一直在参观这些工厂吧。
5. They may have left yesterday. 他们可能昨天已走了。

注：若上句用 might (或 could) 代替 may，则句义变为“他本来是可以（或能够）昨天走的[但实际上他昨天没走]”。必须注意这些用法差别。

A："Whatever has happened to Mary?" 甲：“玛丽究竟出什么事”
B："I don't know. She may have got lost." 乙：“我不知道。她也许迷路了。”

七、“may well + 动词”和“and well + 主语 + may”用法举例在本句型中 well 按 with good reason（有充分理由）或 reasonably（有理地）去理解，就易于记住本句型用法

1. He may well be proud of his success。他有理由为他的成功而自豪。
2. They are proud of their Success, and well they may. 他们为获得成功而自豪，也是应该的。
3. You may well pull down an old house. 你们拆毁旧房是对的。

注：注意“may + 动词 + well”和 "may well + 动词" 的意思不同：She may study well. 她也许觉得很好。（试与上述三例比较。）

八、“主语 + may as well + 动词 + 比喻体 + as + 动词原形 + 本体”用法。这是比较特殊的连接比喻的方式，一般可译为“不妨”或“不如”，含消极口吻，不如 would rather…（宁愿…）或 had better…”（最好…）具有积极语气

1. You may as well call a cat a little tiger as call a tiger a big cat. 你可以把虎叫做大猫，同样也无妨可把猫叫做小老虎。
2. She may just as well go home as not. 她最好是回家去。

注意有时省略后面 as 引导的从句，这时 may as well 相当于 had better 的用法。例如：We may as well set out on our travels. 我们最好出发去旅行。