The Law is a system of rules that regulates the conduct of a community, and it is enforced through penalties. Most countries today have a written constitution that sets the broad framework for their laws, and additional legislation (legislation) is made to fill in the details. The Law is a complex field, covering all aspects of human life and relationships, from criminal and civil justice to property ownership and business contracts.

The laws that a place or authority follows are often based on the culture and social habits of the people in that area, and religious texts can also be influential. The law is also influenced by the philosophies of those who study and create it. For example, utilitarian philosophers such as John Austin and Jeremy Bentham argue that the concept of law encompasses morality, and their theories have been incorporated into legal education and practice. Other lawyers, such as Jean-Jacques Rousseau, believe that the natural law reflects a set of principles that are unchanging and inherent in the universe.

A law may cover all areas of life, from the right to own a gun or not to smoke cigarettes, to the right to marry whomever one wants. The most familiar aspect of the law is that it outlines what is considered a crime and provides punishments for those who break the rules. The law is also used to describe the responsibilities of the government and the structure of its institutions, such as police or courts.

There are several different types of laws, depending on the country and its history. Some nations use a common law system, in which judges determine the rules for cases that come to trial through their own interpretation of past decisions. Other countries use a civil law system, in which statutes clearly state the decisions that judges must follow.

Some specific fields of law include tort (or injury) laws, such as those governing automobile accidents or defamation; business laws, which cover the rules that apply to companies; and competition laws, which are based on Roman decrees against price fixing and English restraint of trade laws from the 19th century. In addition, there are many specialized fields of law, such as the law of international treaties or the law of the sea.

A lawyer is a professional who studies and applies the laws of a country or region. In the United States, the term attorney is commonly used to refer to a person who works in a court of law and prosecutes or defends criminal cases. In the UK, solicitors are attorneys who work in a law firm, while barristers work in the higher courts. The term Esquire is sometimes used to signify a lawyer of distinction. Other terms for the profession are jurist or jurisprudent. Law is a vast subject, covering all aspects of human society, and Oxford Reference provides more than 34,000 concise definitions and in-depth encyclopedic entries to help researchers at every level find the information they need.