In common law, a writ is a formal written order issued by a body with administrative or judicial jurisdiction; in modern usage, this body is generally a court. Warrants, prerogative writs and subpoenas are common types of writ but many forms exist and have existed.
In its earliest form a writ was simply a written order made by the English monarch to a specified person to undertake a specified action; for example, in the feudal era a military summons by the king to one of his tenants-in-chief to appear dressed for battle with retinue at a certain place and time. An early usage survives in the United Kingdom and Canada in a writ of election, which is a written order issued on behalf of the monarch (in Canada, the Governor General) to local officials (High Sheriffs of every county in the historical UK) to hold a general election. Writs were used by the medieval English kings to summon persons to Parliament (then consisting of the House of Lords alone) whose advice was considered valuable or who were particularly influential, who were thereby deemed to have been created "barons by writ".
Writs in English law have a long history, dating back to the medieval period or earlier. Within the court room, specific writs were developed for a variety of different forms of action, until a process of rationalisation took place from 1832-1873. Palgrave's Parliamentary Writs (1827, 1834). shows the variety of writs that had developed prior to this rationalisation.
The development of writs as a means of commencing a court action was a form of "off-the-shelf" justice designed to enable the English law courts to rapidly process lawsuits by allocating each form of complaint into a standard category which could be dealt with by standard procedures. The complainant simply applied to the court for the writ most relevant to his complaint to be sent to the wrongdoer, which ordered him under royal authority to attend a royal court to answer for his actions. The development was part of the establishment of a Court of Common Pleas, for dealing with commonly made complaints by subjects of the crown, for example: "someone has damaged my property". The previous system of justice at the royal court of Chancery was tailor-made to suit each case and was thus highly time-consuming. Thus eventually the obtaining of a writ became necessary, in most cases, to have a case heard in one of the Royal Courts, such as the King's Bench or Common Pleas. Some franchise courts, especially in the Counties Palatine, had their own system of writs which often reflected or anticipated the common law writs. The writ was "served" on (delivered in person to) the wrongdoer and acted as a command that he should appear at a specified time and date before the court specified in the writ, or it might command some other act on the part of the recipient.