Law is a system of rules that a society or a government recognises as regulating the actions of its citizens. It deals with issues such as criminal activity, business agreements, and social relationships. It is a central topic of debate and discussion in philosophy, history, sociology, economic analysis, and political theory. Law is the basis of all governmental activity, and is central to the functioning of any civilised society. It can be used for good or evil, as in the case of dictatorships or military rule, but also to protect minority rights and promote social justice.

The precise definition of law is a matter of dispute, but in general it refers to a set of commands, prohibitions or regulations imposed by authority upon those under its control. It may consist of written or unwritten rules, and can be general or specific. Law can be enforced by a court or by other agencies such as the police. It consists of both positive and negative rules, with positive laws enacting what should be done, and negative laws prohibiting what should not be done.

There are many different kinds of law, depending on the country, its culture and history, and the nature of its governance. In some systems, such as that of the Roman Empire, laws were complex and detailed, but also adaptable to change. In other systems, such as the medieval kingdoms of England and France, law was less formal and more influenced by custom and jurisprudence.

The most common legal systems in the world today are civil law and criminal law, which differ in the subjects covered, and in the way that they are governed. Civil law covers property, contracts and relations between individuals, while criminal law is concerned with a wide range of crimes against the state and public order. Many legal systems also have a third type, religious law, which is based on scriptures.

Law aims to achieve many goals, including maintaining the peace and order, protecting property and privacy, resolving disputes, and promoting social change. Some governments may be more effective at some of these than others. For example, an authoritarian government may keep the peace and maintain the status quo, but it is likely to oppress minorities and its own people, or to have a disastrous effect on the environment (e.g., Burma or Zimbabwe).

The study of law is a rich field for academic inquiry, covering such topics as the relationship between politics and the legal system; the role of religion in the law; the history and development of legal thought, and the relationship between law and ethics. Oxford Reference offers authoritative and accessible encyclopedic entries on these and other topics, with expert guidance from trusted experts. In addition, we provide comprehensive coverage of the main areas of law, with articles on legal terms and concepts, legal history, and major debates in the field. Our articles are written by scholars in their field, and are designed to support research at all levels.