Law is a system of rules that a society or government develops to deal with crimes, business agreements and social relationships. It also encompasses the legal profession, which involves advising and representing people and going to court.

A precise definition of law is difficult to give, as each society has its own approach and a lot of factors influence the principles underlying it. It is generally agreed that the main function of law is to ensure a peaceful existence by establishing a framework of rules which are enforced. It also provides a mechanism by which sanctions can be imposed for breaking these rules.

There are many different kinds of law, depending on the specific needs of a society and the kind of activities that are carried out. Examples include contract law, which regulates agreements to exchange goods or services; intellectual property laws (such as copyright, patent and trademark) that protect creative work; aviation laws, which outline the safety standards for air travel; tort law, which helps people make claims for compensation when they have been hurt by the actions of others; and environmental laws.

The exact process by which law is determined varies from country to country, with civil law systems tending to use legislative statutes and judicial decisions to determine what the law is; common law jurisdictions are more complex, with the principle of stare decisis (meaning that decisions made in previous cases will bind subsequent courts) giving weight to earlier decisions. In some countries, such as the United States and Australia, decisions by the Supreme Court are binding on all lower courts; in other countries, such as most of Europe, higher courts are not bound to follow earlier decisions.

It is important to remember that laws are not simply decided by logic; they reflect a variety of factors including the felt necessities of a particular time and place, the prevalent moral and political theories, intuitions of public policy – avowed or unconscious – and even prejudices shared by judges. Nevertheless, there are some fundamentals that seem to be consistent across societies. These include the notion that it is better to keep the peace than to allow war, and a belief that people have certain rights, which are protected by law.

The study of law is a large and diverse field, covering everything from the study of legal history to debates about constitutional law, international law and the theory of law. Oxford Reference offers comprehensive coverage of all major fields of law, with concise definitions and in-depth, specialist encyclopedic entries written by trusted experts. Our authoritative content includes criminal law, taxation law, employment law and human rights laws, as well as international, constitutional and statutory law. It also covers the broader themes of social justice and ethics in law, as well as major debates in legal theory. It is a valuable resource for anyone who needs to know the law, whether they are studying it at school or need to understand how it works in practice.