Law is the system of rules that a society or government develops in order to deal with crimes, business agreements and social relationships. It is also used to describe the profession of lawyers, judges and other people who work within the legal system.

There are many different ideas about and definitions of law. Some of the main categories are contract law, property law and criminal law. Others include labour law, tax law and administrative law.

Contract law regulates the way that people make agreements about things they want to buy or sell. It covers everything from buying a bus ticket to trading options on the derivatives market. Property law defines a person’s rights and duties towards tangible (real) property like land and buildings, and intangible or ‘personal’ property such as computers and cars. Property law distinguishes between a right in rem which concerns the ownership of an item, and a right in personam which allows compensation for a loss but does not necessarily return a particular thing back. Other forms of property law involve intellectual property such as patents and copyright, trust law (business law) and trademarks.

Crimes are offences against the state and can be a violation of civil or common law. They are punishable by either fines or prison sentences. Criminal laws are enforced by the police and courts, with judges resolving disputes between citizens and deciding whether people accused of crimes are guilty or not. Many countries have a system of appeals courts and a supreme authority that oversees the entire justice system.

The philosophy of law involves debates about the purpose of law and what it should be based on. It is sometimes argued that laws should be purely practical and utilitarian. Others argue that this view of law is too narrow and that at least some laws reflect a moral stance. For example, the prohibition against insider trading may be a protection of fairness, and due process is a fundamental principle that protects people’s rights to a fair trial and treatment by the courts.

Law is often considered to be the bedrock of a democratic society, ensuring that everyone has the same rights and freedoms. However, there are also a number of issues regarding how this concept of law is interpreted and applied in practice. For example, the concept of natural law, developed by Jean-Jacques Rousseau and influenced by Aristotle, suggests that certain principles are universally binding and unchanging. This view has been criticized as being impractical and inflexible, but it is still a significant philosophical influence on the development of law. Other important issues are discussed in the articles on legal system; politics; political party; and ideology. See also: legal education and career; and legal ethics.