Law is a system of rules that a society or government develops to deal with crime, business agreements, social relationships and so on. It also refers to the field of jurisprudence, the profession of being a lawyer. However, the word can also be used more broadly to describe any strong rule that must be followed. A parent’s house rules, for example, might be described as laws. Likewise, something done instinctively or spontaneously might be called a law, like trying to save your own life in a dangerous situation.

Law has many different aspects, and the field of law is huge. A legal expert will usually focus on a specific area of law, such as corporate or criminal law. They may also choose to specialise in a particular subject, such as family or employment law.

Generally, the purpose of law is to control human behaviour and prevent social unrest. It can also serve to promote certain values, such as fairness and order. A nation’s law can be influenced by the culture, political philosophy, economic interests and traditions of its people.

In many societies, law is based on traditional customs and practices. This is known as common law, and it can be a source of legislation as well as judicial decisions. Other law systems, such as civil law, base their legal system on written statutes and executive regulations. The difference between common and civil law is that, in common law systems, judicial decisions are recognised as ‘law’ on equal footing with legislative statutes. This ‘doctrine of precedent’, as it is known, ensures that a court’s decision will be binding on subsequent courts.

Some philosophers have debated whether laws should incorporate a moral position. Utilitarian theories, such as John Austin’s, argued that laws should be “commands, backed by the threat of sanctions, from a sovereign, to whom people have a habit of obedience”. Others, like Hans Kelsen, developed the ‘pure theory of law’ which states that law does not seek to describe what must occur, but only defines rules that individuals must abide by.

Laws cover all manner of subjects, from land and property to a complex set of commercial and personal contracts. Criminal law, for instance, deals with issues of homicide and terrorism. In addition, the legal system covers such diverse topics as aviation law, maritime law, contract law and intellectual property law.