Law is a system of rules that a society develops to deal with crime, business agreements, and social relationships. It can also refer to the profession of those who advise people about the law, represent them in court, give decisions, and punish offenders. This article deals primarily with the laws themselves and their application. For articles about individual types of law, see civil law; criminal law; corporate law; family law; and labor law.

The law is the body of rules imposed by a controlling authority that commands what must be done and prohibits what must not be done. The law may be written or unwritten, but it is always enforced by a power exercised through courts and other tribunals. The law governs everything from private property to public safety, and it sets standards of behavior for citizens.

For the most part, the law is a series of unwritten rules and customs that are enforced through courts and other tribunals. These include rules of evidence, civil procedure, and criminal procedure. The law also covers the rights and duties of a person to his or her neighbors, family members, employers, and other persons. The law also sets standards of conduct for governments and nations.

The legal systems of different countries differ considerably. Some, such as common law, have a centralized judicial branch that interprets and applies general principles. Others, such as Islamic law and Jewish law, are largely self-contained traditions.

Most countries have a mixture of these systems. In the United States, for example, common law and statutes exist side by side. Civil law systems, which are found on all continents except Antarctica, are based on Roman concepts and categories and sometimes supplemented by local custom and culture.

In a country, the law serves several purposes: to keep peace, maintain the status quo, promote social justice, and provide for orderly and gradual social change. Some legal systems serve one or more of these functions better than others.

Laws are enforceable by courts and other tribunals, and they are created by judges. A judge can order the arrest of a person for breaking the law, or can impose a fine or imprisonment on a business or individual that has violated the law. A judge can also set a temporary restraining order that prevents someone from taking an action likely to cause irreparable harm until a hearing can be held. A judge can also issue a criminal charge against someone, or can release convicted offenders on probation if they agree to abide by certain conditions. A judge can also write a legal opinion on an issue or dispute. A court can also record a trial or other proceedings for later use in other cases. A court of appeals can review the decisions of lower courts and appellate judges. A trial is an examination of the facts and law by a judge or jury, often in front of other judges. A retrial is a new hearing in which the verdict of the previous trial can be challenged.