One word in a sentence?

Yes. A verb in the imperative mood (i.e., a command) doesn't take an explicit subject. The second person ("you") is understood. If the verb is used intransitively (i.e., it doesn't convey action to an object), then there won't be an object either. So you may get into your car and say to the chauffeur, "Drive!" and he will understand that you mean "You must put the car in motion."

Thank you for the answer.

Would it be the same, if I don't place an exclamation mark? That is, if I only put a dot?

And secondly, could it be a noun, standing alone like this? With a dot.

Kind regards,
Eva BJ

Yes, you could have a one-verb imperative verb followed by a period/full stop. You dould also have a sentence consisting of a single noun. It would usually be in response to a question. (What do you think that bear wants?" "Us. Run!")

And brevity is paramount when you and a fellow hiker confront a bear. The bad news is that a bear will have no trouble outrunning you. The good news is that you don't have to outrun the bear. You just have to outrun your companion.

Aha! Yes - that makes sense. Thanx