In law, common law, also known as judicial precedent, judge-made law, or case law, is the body of law created by judges and tribunals. Unlike statutory law, the common law is contained and developed within written opinions and judgments. In cases where parties disagree on what the law is, a common law court looks to past decisions of relevant courts, and synthesizes the principles of those past cases as applicable to the current facts. If a similar dispute has been resolved, the court is usually bound to follow the reasoning used in the prior decision (a principle known as stare decisis). If, however, the court finds that the current dispute is fundamentally distinct from all previous cases, and legislative statutes are either silent or ambiguous on the question, judges have the authority and duty to resolve the issue. The court states an opinion that gives reasons for the decision, and those reasons agglomerate with past decisions as precedent to bind future judges and litigants. Common law, as the body of law made by judges, stands in contrast to and on equal footing with statutes, which are adopted through the legislative process, and regulations, which are promulgated by the executive branch.
The common law, so named because it was "common" to all the king's courts across England, originated in the practices of the courts of the English kings in the centuries following the Norman Conquest in 1066. The British Empire later spread the English legal system to its colonies, many of which retain the common law system today. These common law systems are legal systems that give great weight to judicial precedent, and to the style of reasoning inherited from the English legal system. The other major legal system, used in most countries that were not colonised by the English, is the civil law. Civil law systems usually do not regard past judgments and their reasoning binding, instead relying solely on legal codes in judgment.
Today, one-third of the world's population lives in common law jurisdictions or in mixed legal systems that combine the common law with the civil law, including Antigua and Barbuda, Australia, Bahamas, Bangladesh, Barbados, Belize, Botswana, Burma, Cameroon, Canada (except for Quebec), Cyprus, Dominica, Fiji, Ghana, Grenada, Guyana, Hong Kong, India, Ireland, Israel, Jamaica, Kenya, Liberia, Malaysia, Malta, Marshall Islands, Micronesia, Namibia, Nauru, New Zealand, Nigeria, Pakistan, Palau, Papua New Guinea, Philippines, Sierra Leone, Singapore, South Africa, Sri Lanka, Trinidad and Tobago, the United Kingdom (including its overseas territories such as Gibraltar), the United States (except for Louisiana), and Zimbabwe.
In modern usage, common law is contrasted with a number of other terms. First, in denoting the body of judge-made law based on that developed in England… [P]erhaps most commonly within Anglo-American jurisdictions, common law is contrasted with statutory law ...
1. The body of law derived from judicial decisions, rather than from statutes or constitutions; [synonym] CASE LAW [contrast to] STATUTORY LAW.
2. The body of law based on the English legal system, as distinct from a civil-law system; the general Anglo-American system of legal concepts, together with the techniques of applying them, that form the basis of the law in jurisdictions where the system applies...
"common law" is contrasted by comparative jurists to civil law.