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 spread its legal system to its historical colonies, many of which retain the common law system today. These "common law systems" are legal systems that give great precedential weight to common law, and to the style of reasoning inherited from the English legal system.
Today, one-third of the world's population lives in common law jurisdictions or in systems mixed with civil law, including Antigua and Barbuda, Australia, Bahamas, Bangladesh, Barbados, Belize, Botswana, Burma, Cameroon, Canada (both the federal system and all its provinces except Quebec), Cyprus, Dominica, Fiji, Ghana, Grenada, Guyana, Hong Kong, India, Ireland, Israel, Jamaica, Kenya, Liberia, Malaysia, Marshall Islands, Micronesia, Namibia, Nauru, New Zealand, Nigeria, Pakistan, Palau, Papua New Guinea, Sierra Leone, Singapore, South Africa, Sri Lanka, Trinidad and Tobago, the United Kingdom (including its overseas territories such as Gibraltar), the United States (both the federal system and 49 of its 50 states), and Zimbabwe. Some of these countries have variants on common law systems.
The term common law has many connotations. The first three set out here are the most-common usages within the legal community. Other connotations from past centuries are sometimes seen, and are sometimes heard in everyday speech.
The first definition of "common law" given in Black's Law Dictionary, 10th edition, 2014, is "The body of law derived from judicial decisions, rather than from statutes or constitutions; CASELAW, STATUTORY LAW." This usage is given as the first definition in modern legal dictionaries, is characterized as the “most common” usage among legal professionals, and is the usage frequently seen in decisions of courts. In this connotation, "common law" distinguishes the authority that promulgated a law. For example, the law in most Anglo-American jurisdictions includes "statutory law" enacted by a legislature, "regulatory law" (in the U.S.) or “delegated legislation” (in the U.K.) promulgated by executive branch agencies pursuant to delegation of rule-making authority from the legislature, and common law or "case law", i.e., decisions issued by courts (or quasi-judicial tribunals within agencies). This first connotation can be further differentiated into
Publication of decisions, and indexing, is essential to the development of common law, and thus governments and private publishers publish law reports. While all decisions in common law jurisdictions are precedent (at varying levels and scope as discussed throughout the article on precedent), some become "leading cases" or "landmark decisions" that are cited especially often.