An imperative sentence gives anything from a command or order, to a request, direction, or instruction. Imperative sentences are more intentional than exclamatory sentences and do require an audience; as their aim is to get the person(s) being addressed either to do or to not do something. And although this function usually deals with the immediate temporal vicinity, its scope can be extended, i.e. you can order somebody to move out as soon as you find yourself a job. The negative imperative can also be called the prohibitive and the inclusive plural imperative, the hortative. It is debatable whether the imperative is only truly possible in the second person. The vocative case of nouns can be said to indicate the imperative as well since it does not seek information, but rather a reaction from the one being addressed. An imperative can end in either a period or an exclamation point depending on delivery.
This is a companion discussion topic for the original entry at http://grammarerror.com/tags/imperative-sentence