Law is commonly understood as a system of rules that are created and enforced through social or governmental institutions to regulate conduct, although its precise definition is a matter of longstanding debate. It has been variously described as a science and the art of justice.

State-enforced laws can be made by a collective legislature or by a single legislator, resulting in statutes, by the executive through decrees and regulations, or established by judges through precedent, normally in common law jurisdictions. Private individuals can create legally binding contracts, including arbitration agreements that may elect to accept alternative arbitration to the normal court process. The formation of laws themselves may be influenced by a constitution, written or tacit, and the rights encoded therein. The law shapes politics, economics, history and society in various ways and serves as a mediator of relations between people.

Legal systems vary between countries, with their differences analysed in comparative law. In civil law jurisdictions, a legislature or other central body codifies and consolidates the law. In common law systems, judges make binding case law through precedent, although on occasion case law may be overturned by a higher court or the legislature. Historically, religious law influenced secular matters, and is still used in some religious communities.Sharia law based on Islamic principles is used as the primary legal system in several countries, including Iran and Saudi Arabia.

Law's scope can be divided into two domains. Public law concerns government and society, including constitutional law, administrative law, and criminal law. Private law deals with legal disputes between individuals and/or organisations in areas such as contracts, property, torts/delicts and commercial law.This distinction is stronger in civil law countries, particularly those with a separate system of administrative courts;by contrast, the public-private law divide is less pronounced in common law jurisdictions.