Law is a collection of rules that regulates the relationships among individuals and groups within society. It covers topics such as criminal law, which punishes people for committing crimes; civil law, which resolves lawsuits (disputes); and administrative law, which governs the administration of government. It also provides a source of scholarly inquiry into legal history, philosophy and economic analysis, and raises important and complex issues concerning equality and fairness.

Whether governing a single nation-state or a multinational corporation, the primary function of law is to ensure that everyone abides by the agreed upon social norms and that the rights of citizens are respected and protected. In the case of a nation, this is accomplished by means of constitutional or political structures and a system of laws and courts. The structure of these systems varies widely from one country to another; each country has its own historical and cultural influences that determine how law is made and enforced.

In many societies, law is based on religious precepts, such as Jewish halakha or Islamic Shari’a. In such cases, the religion acts as an authoritative interpreter of the law via a process of qiyas (reasoning by analogy) and ijma (consensus), and the laws are often codified in religious texts such as the Quran or Talmud. Despite this religious basis, most modern legal systems have secularized and placed greater emphasis on the protection of individual freedoms.

The subjects of law cover virtually every aspect of human life, but the core areas are civil, criminal and employment law. Civil law, also known as continental law, is found on all continents except Antarctica and is based on the categories, concepts and rules of Roman or Romano-Germanic law, sometimes supplemented with local culture and custom. Criminal law is a branch of public law that deals with the punishment of alleged criminals for their actions, while employment law refers to the tripartite industrial relationship between employee, employer and trade union.

Other branches of the law include commercial law, property law and family law. Commercial law encompasses regulations that govern free movement of goods and services; it may be applied to international commerce. Property law includes the rules governing ownership and possession of real estate, as well as legal rights to intellectual property, such as patents and copyrights. Family law covers marriage, divorce, child custody and parental rights. Space law is a recent development that addresses the implications of humans in Earth orbit and outer space. This is a rapidly developing area that requires collaboration with scientists, engineers and astronauts. Law is also used in the practice of law, which involves advising clients and representing them in court. This practice of law is typically regulated by government or an independent regulating body such as a bar association or law society, and lawyers obtain a distinct professional identity through specified procedures and a legal education that results in a degree such as a Bachelor of Laws or a Juris Doctor degree.