表示请求或命令别人做某事或不做某事。
1）用于第二人称，通常省略you。
①肯定祈使句：Open the door, please.
②否定祈使句：Don’t be late again.
2）用于第一人称和第三人称，通常以let（let后跟宾格）或shall开头。
Let me have a look. Let’s play a game now. Let him go home now.
Shall we meet at one thirty in front of the Garden Theatre?
。