Law is the system of rules that a particular country or community recognizes as regulating the actions of its members. The study of law includes the history, development, and organization of legal systems, as well as major debates in legal theory. Oxford Reference offers more than 34,000 concise definitions and in-depth, specialist encyclopedic entries across this broad discipline-from criminal, tax, and social security law to international, family, and employment law, and beyond.

Most modern societies have laws governing the behavior of its citizens. These may be written or unwritten, but they are designed to ensure a peaceful society and that those who violate the law face consequences for their actions. This is achieved through a complex network of institutions that includes the state, courts, and a civil society.

Generally speaking, there are three main types of laws: criminal, administrative, and constitutional. Criminal law concerns the punishment of those who commit crimes, administrative law regulates public policies and procedures, while constitutional law is concerned with the overall structure of a country’s government.

The complexity of law reflects its vast range of applications in a society. For example, contract law governs agreements that exchange goods or services, including everything from buying a bus ticket to trading options on a derivatives market. Property law defines people’s rights and duties toward tangible property, such as land or buildings, and movable possessions, like computers, cars and jewellery. Intellectual property is governed by patent and copyright law, while the law relating to money and business transactions is known as commercial or transactional law.

In addition to these general areas of law, there are many specific branches of it. Immigration and citizenship law concern a person’s right to live and work in a country that is not their own, while the law governing marriage and divorce proceedings lies within family law. Corporate and commercial law deals with the way in which companies and individuals operate, while biolaw is the intersection of law and the life sciences.

The development of law in a society depends on how its institutions are organized. As James Madison wrote in the Federalist Papers, “a government of men over men must necessarily be a government of limited powers.” This principle, called separation of powers, was built into the U.S. Constitution by separating the legislative, executive, and judicial branches of government. However, this principle does not apply to all political systems. Some, such as parliamentary democracies, combine the power of the legislative, executive and judicial branches into one body, requiring that it be monitored through regular elections and mechanisms such as no confidence votes. In such cases, the rule of law is less secure.