The counties of the United Kingdom are subnational divisions of the United Kingdom, used for the purposes of administrative, geographical and political demarcation. The older term, shire is historically equivalent to county. By the Middle Ages, county had become established as the unit of local government, at least in England. By the early 17th century, all of England, Wales, Scotland, and Ireland had been separated into counties. In Scotland shire was the only term used until after the Act of Union 1707. Since the early 19th century, counties have been adapted to meet new administrative and political requirements, and the word county (often with a qualifier) has been used in different senses for different purposes. In some areas of England and Wales, counties still perform the functions of modern local government. In other parts of the United Kingdom, especially within large metropolitan areas, they have been replaced with alternative unitary authorities, which are considered 'county level' authorities. Today, these have largely replaced the historic county corporate entities granted self-governance with county government powers. Today, in addition to local government counties, every part of the United Kingdom lies within the historic counties which have formed geographic and cultural units since the Middle Ages. Additionally, there are vice-counties, which are geographic areas based on the historic counties, and used in scientific data gathering. Their purpose is to maintain the stability of the geographic area for scientific studies, and thus ignore changes in political demarcations. England England is divided into 48 ceremonial counties, which are also known as geographic counties. Many of these counties have their basis in the 39 historic counties whose origins lie in antiquity, although some were established as recently as 1974. Outside Greater London and the Isles of Scilly, England is also divided into 83 metropolitan and non-metropolitan counties. These correspond to areas used for the purposes of local government and may consist of a single district or be divided into several. As of April 2009, 27 such counties are divided into districts and have a county council. Most ceremonial counties correspond to a metropolitan or non-metropolitan county of the same name, but often with reduced boundaries. The current arrangement is the result of incremental reform; from 1974 to 1996 the metropolitan and non-metropolitan counties corresponded directly with the ceremonial counties. From 1889 to 1974 areas with county councils were known as administrative counties and ceremonial counties were defined