Law is a complex subject which touches on a huge variety of aspects of life. Three broad categories are presented below, though the subjects often overlap and intertwine. Contract law involves agreements to exchange goods and services; property law deals with people’s rights toward tangible items (like land or cars) and intangible items like bank accounts and shares of stock; criminal and civil procedure concerns the rules that must be followed as trial and appeals are conducted.

The precise nature of the law is difficult to pin down, but it is generally accepted that it comprises precepts of some kind, and that it governs behaviour in a way which aims to promote social stability. The law shapes politics, economics and history, as well as defining human relationships and the way societies are run.

Laws are developed in a wide range of ways, from written laws passed by legislatures, to a system of common law which relies on judge-made precedent. The law can also encompass the rules and customs that a society or group of societies establishes in order to govern its relationships: this is sometimes called cultural law.

A major branch of law is criminal law, which punishes conduct that is considered harmful to public safety and morality, such as murder, robbery, fraud or false advertising. Another major area is civil law, which deals with lawsuits between individuals. The broader field of business law includes areas such as tax law, company law and banking regulation.

International law covers international treaties and legal disputes, particularly those that affect more than one country or region. It is increasingly concerned with global issues such as environmental law and the law of international watercourses. Space law is a recent development, dealing with the laws and policies that govern activities in Earth orbit and outer space.

In the earliest times, laws were largely oral and local, but with the rise of the Roman empire there was a move towards written codification. These Roman codes were adapted by medieval legal scholars and incorporated into English law, as well as into the systems of European civil law which became dominant after 1750.

The law is an important subject for scholarly research in areas such as legal history, philosophy and economic analysis. It is a vital part of modern life and raises important ethical questions about equality, fairness and justice. It is also the subject of much speculative and ideological discussion, as well as providing a basis for practical action. The study of law is usually a component of legal training and the profession of lawyering. It is possible to achieve a degree in law, either through an undergraduate qualification such as a Bachelor of Laws or a higher degree such as a Master of Laws. Lawyers are required to follow specific professional procedures and be regulated by a professional body such as a bar association or law society in most jurisdictions. They must also keep up to date with changes in the law.