Writ

A writ is a judicial order commanding a person to do something. An example is the writ of certiorari, which is issued by the U.S. Supreme Court to a lower court to reconsider its decision on appeal.

There are four types of writs in the United States federal courts:

* habeas corpus
* certiorari
* mandamus
* prohibition

Rule 21 of the Federal Rule of Appellate Procedure 21 addresses the latter two.