Law is the system of rules that a particular community recognizes as regulating the actions of its members. Oxford Reference offers expert-level, trusted definitions and in-depth, specialist encyclopedic entries on all aspects of this broad discipline—from criminal, tax, social security, and family law to international, human rights, and legal theory.

Laws set out what is permissible and impermissible in society, defining property, contracts, and other important rights. They also govern the conduct of public and private actors, including government officials, police, and judges. In a well-functioning democracy, laws ensure that everyone has the same opportunities and freedoms—and their duties are carried out in a fair, equitable, and efficient manner.

In addition to protecting personal and property rights, laws can protect public health, safety, and the environment. They regulate a wide range of activities, from smoking and drinking to importing and exporting goods, driving, and working for hire. They can even determine how to resolve disputes over such issues as who owns a piece of land.

The law consists of the statutes, regulations, and decisions of courts and administrative agencies. It also includes the constitution, which establishes the basic structure of a nation-state, and the rules that govern political parties, elections, and referendums. It may also include the charter of a corporation or the principles governing a union.

From a methodological viewpoint, the study of law is complex. It is distinct from other sciences, such as natural science (as in the law of gravity), or social science (such as the laws of supply and demand). Law is normative rather than descriptive and prescriptive; it sets out what people ought to do and prohibits them from doing certain things.

Law plays an influential role in politics, economics, history, and society. It shapes the way we think and act, as it mediates our relations with others. It is the primary means of resolving conflicts between individuals and between nations.

Legal systems are broadly divided into civil law and common law. The former are found throughout the world and are based on categories and rules, often supplemented by cultural or customary factors. The latter are more numerous in the Western world, but can also be found in some religious communities, especially those that follow Islamic Shari’ah. Other types of law are also in use, such as canon law and Jewish Talmudic law. For more on the relationship between law and power, see democracy; governance; human rights; and rule of law. For more on legal institutions, see court; lawyer; judge; jury; and jurisprudence. See also criminal law; tort; and property.