What do you call a command or order given in speech or writing?

The term that refers to a command or order given in speech or writing is "imperative." In linguistics, imperative sentences are those that issue commands, requests, or instructions, typically using the base form of a verb. For example, "Close the door" is an imperative sentence directing someone to perform an action. This grammatical mood is essential in conveying direct instructions clearly and effectively.

The other choices focus on different language features. A cliché refers to an overused expression that has lost its original meaning, making it less impactful or meaningful. A rhetorical question is a figure of speech where a question is posed for effect rather than to elicit an answer, often to provoke thought or emphasize a point. Archaism refers to a word or phrase that is outdated and no longer in common use. Each of these terms serves a different function in language and does not relate to the concept of issuing commands or orders.