Law is the set of rules created by a sovereign power that forms the framework to ensure a peaceful society and to punish those who break the rules. A society can use law to govern itself in a variety of ways, from regulating the exchange of goods and services (contract law) to determining who has the right to control land and property. The law can also serve a number of social functions, including promoting morality and maintaining order.

Law consists of a wide range of subjects and disciplines, from the study of how courts work (courts and legal procedure) to the laws of biology and chemistry (biolaw). The field has many subtopics, which are discussed in articles related to specific fields. For example, employment law relates to the legal rights of workers and employers; family law discusses the legal rights of families; immigration law and nationality law discuss the rules for living in a country other than one’s own; and property law covers the concepts of ownership and transfer of title to tangible assets such as houses and cars, as well as intangible assets such as bank accounts and shares of stock.

A wide-ranging debate about the nature of the law has taken place over the centuries. A prominent early argument was made by Hans Kelsen in his Pure Theory of Law, which argued that the law did not seek to describe what must occur; rather, it defined the rules that individuals had to follow if they were to live in harmony with others. More recent debates have focused on the extent to which the concept of law encompasses morality. For example, John Austin’s utilitarian definition of law was that it was “commands backed by the threat of sanctions from a sovereign to which people have a habit of obedience.” Others, such as Jean-Jacques Rousseau and Thomas Aquinas, argued that the idea of law reflected a set of unchanging laws of human nature.

The application of law varies widely across the globe. Countries with civil law systems (which include most of the world’s population) base their laws on ideas, categories, and rules inherited from Roman law and canon law, sometimes supplemented or modified by local custom and culture. The common law tradition in the English-speaking world uses a different approach, based on precedent and the articulation of principles through judicial decisions. Other legal traditions are religious, such as the Shari’ah in Islam, or a mix of secular and religious ideas, such as the East Asian legal tradition, which uses common law and the Japanese civil code. The law is also used to regulate a variety of activities, from sports to business transactions. The study of the law is often called the practice of law or jurisprudence. Lawyers are trained to advise people about the law and represent them in court cases, and a career in the law is becoming increasingly attractive to young people. Other professions that involve the study of law are public defenders, judges, and police officers.