A brief is a written legal document filed in a litigation or arbitration dispute resolution proceeding in which a party to the dispute recites the facts and the law applicable to the dispute and explains to the court or arbitrator why the party should prevail in the dispute. Courts often have rules regarding the page limits and format for briefs, as well as the method for filing briefs (usually electronically) and delivery of a copies to other parties to the litigation.

In Missouri, a brief is a formal document submitted to a court, arbitrator, or other judicial body during litigation or arbitration. It presents the party's arguments, cites relevant laws and precedents, and explains why the party believes they should win the case. Missouri courts have specific rules regarding the preparation and submission of briefs, which include guidelines on page limits, formatting, and the required content. For instance, the Missouri Rules of Civil Procedure outline the requirements for briefs in civil cases, while the Missouri Rules of Criminal Procedure do the same for criminal cases. Additionally, Missouri courts have embraced electronic filing (e-filing) systems, which allow attorneys to submit briefs and other legal documents online. The rules also stipulate how and when copies of the briefs must be served on the opposing parties. Attorneys practicing in Missouri must adhere to these rules to ensure their briefs are accepted by the court and considered in the decision-making process.