Law is the set of rules and customs established by a community to regulate its members, enforce rights and privileges, and ensure social order. It can be formally written, as in a constitution or statute or unwritten, as in a common law system based on judge-made precedent. There are many types of law, such as contract law, property law, and criminal law. Law can also cover the rights of individuals, such as the right to privacy and the right to freedom from discrimination.

Law shapes politics, economics, history and society in a variety of ways. It is a part of the legal system and is an important mediator between people and groups. It can be influenced by religion, as well as by science and technology, as in the laws of physics or the laws of biology.

The earliest legal systems arose from the need to govern people and their interactions with each other, and with nature. They were influenced by Greek philosophy, but later they underwent considerable codification and specialised training of professional jurists. The result was a very detailed system of law, such as the Roman code or the medieval English royal courts. Laws can be sourced from written sources, as in a constitution or statute or, more generally, from precedent – as in common law systems based on judge-made precedent or, as in the case of some religious systems, from the Bible.

There are many areas of law, such as contract law, which covers all agreements that impose obligations, such as contracts between employers and employees, between parents and their children or between private individuals. Property law outlines people’s rights and duties toward their tangible and intangible property, such as land or buildings, and personal possessions, including bank accounts and shares of stock. Criminal law deals with the rights of a person accused of a crime and their protection by the state.

In addition to the formal law making process, there are many areas of law that are less formally regulated, and may be dealt with by informal methods such as negotiation or arbitration. Some of these are the rules governing the use of copyrighted material, the terms of employment, and the responsibilities of companies that provide services such as water and electricity.

One major challenge in developing a theory of law is that it is impossible to empirically prove what the contents of the law are. This is because, unlike scientific theories or the principles of logic, law can compel behaviours that are beyond the capability of human beings, and it can mandate beliefs that contradict other people’s perceptions of reality. This dichotomy between the law as understood by humans and the law as viewed by nature is at the heart of modern conflict about what constitutes law. There are a number of cultures that have a non-modern concept of law, and some scholars are investigating whether these may offer insights into a unified concept of law.