Law is a system of rules that a society develops to regulate behaviour, protect people and property, and resolve disputes. It is enforced by a state through mechanisms like police and courts. People who break the law can be punished, for example by paying a fine or going to jail. Laws cover a wide range of topics, from the rights of workers to the rules of aviation and medicine. They are often based on religion, custom and social norms. Law is an important part of the fabric of societies and shapes politics, history, economics and social life.

There is no one definition of what law is, and different countries have different laws. Most have a constitution to set the framework and other laws that cover more specific matters. Some common aspects of laws are that they set out what is considered fair or unfair, and that people must follow them. The law is generally enacted (created) by the elected representatives of a country, a legislature, which result in statutes or other legal instruments; by an executive through decrees or regulations; or by judges through their rulings on cases brought before them, known as caselaw.

The different branches of the law are mainly concerned with the rights and duties of citizens and businesses, but they may also relate to how a state functions. Criminal law focuses on the penalties for breaking the law, while civil law relates to disputes between two or more parties. The law also sets out the ways in which courts operate, and what evidence can be used in court.

International law is concerned with the way in which countries interact with each other, such as trade agreements and military actions. There are various international treaties and conventions, which include the Geneva Conventions on the conduct of war, and the Roerich Pact on cultural heritage.

The law has many different purposes, but the four main ones are establishing standards, maintaining order, resolving disputes and protecting liberties and rights. For example, the law can establish minimum wage requirements and health and safety guidelines in the workplace. The law can also protect the intellectual property of people, such as their art or music. In this case, the law protects their work by creating a kind of copyright that prevents other people from using it without permission. The law can also help people protect their property, by setting out the rules for ownership of things like land and buildings. The law can even protect the environment by regulating polluting activities and penalising those who do not comply with environmental regulations. Laws can also be influenced by culture and social norms, and in some cases by religious texts such as the Vedas or the Bible. The law also varies by country, with some cultures having different legal traditions that are not compatible with the Western legal tradition. A professional who studies and practises the law is called a lawyer, jurist or attorney.