What is a written order from a court that requires a person to appear in court?

The correct answer is a summons. A summons is a legal document issued by a court that notifies an individual that they are required to appear before the court, typically in relation to a legal proceeding. This order is crucial as it initiates the legal process and ensures that parties involved have the opportunity to present their case.

In the context of the other options, a subpoena is specifically used to compel a person to testify or provide evidence in a court case, but it does not generally require the individual's appearance in court itself unless explicitly stated. A citation is often issued by law enforcement to cite an individual for a violation of law, requiring them to respond in some way, but it does not serve the same function as a summons in court appearances. A writ is a formal order issued by a court commanding the performance of a specific act or the delivery of a specific person or thing, but it is not exclusively intended to summon an individual to court for a proceeding.

Thus, understanding the specific roles and definitions of these legal terms clarifies why a summons is the appropriate choice for the requirement to appear in court.