The law is a set of rules that regulate human behaviour and define rights and duties. It is a system of rules established by social or governmental institutions and enforced through the mechanisms of the state (such as courts, police, and armies). In modern Western society, it covers such things as property, contracts, criminal justice, and family affairs. The precise nature of law is debated: it is often described as a science, an art, or both, and there are many different types of legal systems.

The idea of the law as a body of principles is usually linked to the notion of morality. For example, an act of war is illegal if it violates international law. However, in general, the term ‘law’ can also refer to any kind of enforceable rule or guideline that regulates human behaviour: e.g. a company’s code of conduct or a religious commandment.

A central idea of law is the principle of justice, which dictates that each individual must be treated equally by the state and should receive a fair trial when accused of a crime. This concept of justice is widely discussed in legal philosophy and literature. The precise definition of justice is a matter of debate, but it usually includes concepts such as fairness, equity, and the non-discrimination of any group or individual.

Some laws are enacted by legislatures, while others originate from judicial decisions or treaties. Many countries have a mixture of both forms of law. Law is also used as a term to refer to the profession of lawyers, who specialise in advising clients and representing them in court.

There are many fields of law, such as bankruptcy, civil and criminal procedure, evidence, banking, and tax law. Each of these fields has its own terminology:

For example, the term ‘brief’ is a written, word-for-word record of what was said in a court case or other proceeding. The term ‘injunction’ is a type of legal order that prohibits someone from doing something and lasts only until a hearing can be held. A ‘precedent’ is a decision made in a previous case with facts and law similar to a dispute currently before a court. Precedents are usually binding, meaning that the court must follow them unless there is a good reason to disagree with them.

There are also laws relating to particular issues, such as immigration, family law, and commercial law. Immigration law deals with the right to live and work in a country that is not your own, while nationality law addresses the issue of citizenship and statelessness. Family law includes proceedings such as divorce, and also concerns the rights of children and spouses to property and money. Commercial law, on the other hand, relates to businesses and financial transactions. A common form of legal dispute is a lawsuit. There are a number of procedures for settling such disputes, including trials and arbitrations. Other terms that are used in the field of law include: