‘Authorities’ considers how the rules of usage are established. It first describes the role of dictionaries, frequently held to be the ultimate authority. It then discusses linguistic academies, governing bodies that make pronouncements about correct usage. An alternative source to the dictionary is the usage guide, which tends to adopt a more prescriptive approach and which focuses on a small subset of frequently disputed points of usage. Other ways of determining acceptability is to turn to examples of actual usage, logic, or etymology. Despite the many controversies concerning correct usage and how it should be established, each of the authorities discussed would agree that there is a single authoritative form of the language, known as Standard English.