The place-names of Wales derive in most cases from the Welsh language, but have also been influenced by linguistic contact with the Romans, Anglo-Saxons, Vikings, Anglo-Normans and modern English. Toponymy in Wales reveals significant features of the country's history and geography, as well as the development of the Welsh language. Its study is promoted by the Welsh Place-Name Society (). History During the 4th to 11th centuries, while Anglo-Saxons and other migrants from Europe settled adjoining areas of Britain, Wales developed as a distinctive entity, developing its language, culture, legal code, and political structures. By stages between the 11th and 16th centuries, Wales was then subdued, conquered and eventually incorporated into the Kingdom of England while still retaining many distinct cultural features, most notably its language. Since then, there has been a mixing of cultures in Wales, with the English language dominant in industry and commerce, but with Welsh remaining as a living language, particularly in its stronghold, y Fro Gymraeg or "Welsh language country" in northwest, mid- and west Wales. Welsh culture and political autonomy has been reasserted increasingly since the mid 19th century. Language characteristics The Welsh language is a Western Brittonic language descended from the Common Brittonic spoken throughout Britain in the centuries before the Anglo-Saxon and Viking invasions that led to the creation of England. Many place-names in Britain, particularly of natural features such as rivers and hills, derive directly from Common Brittonic. Obvious examples of place-names of Welsh origin include Penrith ("headland by the ford") and the numerous Rivers Avon, from the Welsh afon ("river"). Place-names from the Western Brittonic-speaking Hen Ogledd occur in Cumbria and the Scottish Lowlands. These include the name of Edinburgh, from Cumbric Din Eidin "Eidin's Fort". The Cornish language is a Southwestern Brittonic language and many place-names in Cornwall and to a lesser extent neighbouring Devon, Somerset and Dorset therefore have similar origins to names in Wales, such as the River Avon, Devon. The settlement name Tre- is identical to that used in Welsh and is among the most common placename elements in both Wales and Cornwall equating to English -ton, alongside Lan- equating to Welsh Llan- combined with the name of a Saint. In Devon the prevalent use of -combe reflects an early English borrowing of Cornish/Welsh cwm. Welsh remains a living language, spoken by over 20% of the country's population. Like all languages, it has changed over time