Law is a body of rules that regulates the conduct of a society. These laws are enforced by state mechanisms, and sanctions can be imposed for violations. In the broadest sense, law includes all the customs and practices that a community recognizes as binding upon its members. However, legal systems vary considerably in how they define and classify the various subjects of law. The traditional core subjects include criminal law, contract law, constitutional law, property law, tort law, and trusts.

Various theories about the nature of law have been put forward. One important idea is that law reflects a moral order of the universe. Other ideas are that the nature of law is social, and that laws impose coercive force. These concepts have helped to shape different legal systems.

In modern times, law has become central to the functioning of a state. The law identifies the rights and responsibilities of individuals in a nation, while also protecting minorities from majorities and encouraging orderly social change. A system of law is not a panacea, however. While a government based on the rule of law can keep peace and promote order, it may still oppress minorities and impose its will on its citizens.

Laws can be made by legislative groups, resulting in statutes; by executive decrees and regulations; or by judges through the doctrine of precedent (stare decisis). The laws of religion, including Jewish halakha and Islamic Sharia, and the Christian canon are examples of religious law.