described as a principality of the United Kingdom. The title of Prince of Wales is usually given to the heir apparent to the British throne but it has no official political or other role in respect of Wales (though since the early 20th century Princes of Wales have preferentially taken on ceremonial royal duties in Wales on an informal basis). The International Organization for Standardization (ISO) has defined Wales as a "country" rather than a "principality" since 2011, following a recommendation by the British Standards Institute and the Welsh Government. Northern Ireland is sometimes described by United Kingdom citizens as a province of the United Kingdom, which derives from the Irish province of Ulster, of which Northern Ireland is a part. Northern Ireland also had, until 1972, a far greater degree of self-government than the other constituent parts of the UK. Great Britain is both a geographical and a political entity. Geographically, it is one island, but as a political entity it also includes the smaller offshore islands that are administered as part of its constituent nations – England, Wales and Scotland – such as England's Isle of Wight, Wales' Anglesey and Scotland's Inner Hebrides, Outer Hebrides, Orkney Islands and Shetland Islands. The abbreviation GB is sometimes officially used for the United Kingdom, for example in the Olympics, or as the vehicle registration plate country identification code for UK-registered cars (see also British car number plates). SCO for Scotland, CYM for Wales (Cymru), NI for Northern Ireland, or ENG for England can also be used. From 28 September 2021, UK will be the official country code on car registration plates. The internet code .gb, although allocated to the UK, is virtually unused and UK web domains use .uk. Though is the United Kingdom's ISO 3166-1 alpha-2 code, is exceptionally reserved for the United Kingdom on the request of the country. The four constituent parts of the UK are also known, particularly in sporting contexts, as Home Nations or the "Four Nations". The BBC refers to its UK-wide broadcasting operation as Nations and Regions ("regions" referring to geographic regions of England. Thus the naming conventions tend towards describing distinct regions or nations which exist within a single sovereign state. In sport, the home nations mostly have their own separate national teams – England, Wales, Scotland, Northern Ireland, for example in association football. Sporting contests between the Four Nations are known as