祈使句用以表達命令，要求，請求，勸告等。

　　1) 祈使句有兩種類型，一種是以動詞原形開頭，在動詞原形之前加do (但只限于省略第二人稱主語的句子)。

　　Take this seat.

　　Do be careful.

　　否定結構：

　　Don't move.

　　Don't be late.

　　2) 第二種祈使句以let開頭。

　　Let 的反意疑問句

　　a. Let's 包括說話者

　　Let's have another try，shall we / shan't we?= Shall we have another try?

　　b.　Let us 不包括說話者

　　Let us have another try，will you / won't you?= Will you please let us have another try?

　　否定結構：

　　Let's not talk of that matter.

　　Let us not talk of that matter.