英汉词典

1. 极重要的;必要的;紧急的
    If it is imperative that something is done, that thing is extremely important and must be done.

    e.g. It was imperative that he act as naturally as possible...
           最重要的是他要做到尽可能自然。
    e.g. That's why it is imperative to know what your rights are at such a time...
           这就是为什么你有必要在这个时候知道你的权利有哪些。

2. 必要的事;紧急的事;必须履行的责任
    An imperative is something that is extremely important and must be done.

    e.g. The most important political imperative is to limit the number of US casualties.
           现在的头等政治大事就是要控制美国人的伤亡人数。
    e.g. ...the needs of those unable to respond to the imperatives of an enterprise culture.
           那些不能积极响应企业文化核心要求的人的需求

3. 祈使语气
    In grammar, a clause that is in the imperative, or in the imperative mood, contains the base form of a verb and usually has no subject. Examples are 'Go away' and 'Please be careful'. Clauses of this kind are typically used to tell someone to do something.

4. 祈使语气动词
    An imperative is a verb in the base form that is used, usually without a subject, in an imperative clause.