祈使语气(imperative mood) 是表达直接命令或请求的语气。它还用来表示禁止、请求或任何其他类的劝告。/

英语的祈使语气是简单地使用动词不定式来形成的。be 是其非限定形式，是不同于第二人称现在时直陈语气形式的唯一动词。句子的主语只能是 you(第二人称)。其他语言如拉丁语、法语和德语有多种词形变化的祈使语气形式，它们依据如下文法范畴而改变:

例如，拉丁语的正规形式是:

这幺丰富的形式对于更好的理解是有用的，特别是因为祈使语气通常不指定主语代词。

The imperative is a grammatical mood that forms commands or requests, including the giving of prohibition or permission, or any other kind of advice or exhortation.

An example of a verb in the imperative mood is be in the English sentence "Please be quiet". Imperatives of this type imply a second-person subject (you); some languages also have first- and third-person imperatives, with the meaning of "let's (do something)" or "let him/her/them (do something)" (these forms may alternatively be called cohortative and jussive).