Law is a set of rules that are created and enforced through social or governmental institutions to regulate behavior. It has been described as a science and as the art of justice.

In general, legal systems are geared to serve four main purposes: establishing standards, maintaining order, resolving disputes and protecting liberty and rights. Different nations and societies approach these tasks differently. Some have more success than others. For example, a nation ruled by an authoritarian dictatorship may keep the peace and maintain the status quo, but it will often oppress minorities and impede social change. Other nations, such as the United States, have a long history of promoting civil liberties and limiting government power.

There are numerous types of law that have been defined and categorized over the centuries, with many of them overlapping or intersecting with each other. Common subjects include labour law, family law, contract law and criminal law. However, the subject is so broad that it would be impossible to cover all aspects in a single article. The term law is also used to refer to a particular set of laws, such as the Constitution, or the body of legislation and regulations that governs a country or region.

Some law is derived from religious precepts, such as Jewish Halakha and Islamic Sharia, while Christian canon law survives in some church communities. Other legal systems are based on scientific principles, such as the law of gravity or the law of supply and demand.

In common law countries, the decisions of higher courts bind lower courts in future cases, a principle known as stare decisis. However, judicial decision making is not an objective process. The judges and barristers that make up the judiciary are influenced by their personal beliefs, experience and biases. They are also governed by the societal and cultural norms of their jurisdiction, which can influence how they interpret and apply the law.

The resulting mixture of societal and cultural influences means that the precise definition of law is complex from a methodological standpoint. The fact that legal statements are of a normative, rather than descriptive or causal, nature further complicates matters. As a result, the concept of law has been variously described as an art, a science and a moral philosophy.