The modern Celts are a related group of ethnicities who share similar Celtic languages and artistic histories, who live in or descend from one of the regions on the western extremities of Europe populated by the Celts. A modern Celtic identity emerged in Western Europe following the identification of the native peoples of the Atlantic fringe as Celts by Edward Lhuyd in the 18th century. Lhuyd and others equated the Celts described by Greco-Roman writers with the pre-Roman peoples of France, Great Britain and Ireland, they categorised the ancient British languages as Celtic languages. The descendants of these ancient languages are the Brittonic and Gaelic languages, the people who speak them are considered modern Celts; the concept of modern Celtic identity evolved during the course of the 19th century into the Celtic Revival. By the late 19th century, it took the form of ethnic nationalism within the United Kingdom of Great Britain and Ireland, where the Irish Home Rule Movement resulted in the secession of the Irish Free State, in 1922.
There were significant Welsh and Breton nationalist movements, giving rise to the concept of Celtic nations. After World War II, the focus of the Celtic movement shifted to linguistic revival and protectionism, e.g. with the foundation of the Celtic League in 1961, dedicated to preserving the surviving Celtic languages. The Celtic revival led to the emergence of musical and artistic styles identified as Celtic. Music drew on folk traditions within the Celtic nations. Art drew on decorative styles associated with the ancient Celts and with early medieval Celtic Christianity, along with folk-styles. Cultural events to promote "inter-Celtic" cultural exchange emerged. In the late 20th century some authors criticised the idea of modern Celtic identity by downplaying the value of the linguistic component in defining culture and cultural connection, sometimes arguing that there never was a common Celtic culture in ancient times; these authors opposed language preservation efforts. Malcolm Chapman's 1992 book The Celts: The Construction of a Myth led to what the archaeologist, Barry Cunliffe has called a "politically correct disdain for the use of'Celt'" Traditionally, the essential defining criterion of Celticity is seen as peoples and countries that do, or once did, use Celtic languages and it is asserted that an index of connectedness to the Celtic languages has to be borne in mind before branching out into other cultural domains.
Another approach to defining the Celts is the contemporary inclusive and associative definition used by Vincent and Ruth Megaw and Raimund Karl that a Celt is someone who uses a Celtic language or produces or uses a distinctive Celtic cultural expression or has been referred to as a Celt in historical materials or has identified themselves or been identified by others as a Celt or has a demonstrated descent from the Celts. Since the Enlightenment, the term Celtic has been applied to a wide variety of peoples and cultural traits present and past. Today, Celtic is used to describe people of the Celtic nations and their respective cultures and languages. Except for the Bretons, all groups mentioned have been subject to strong Anglicisation since the Early Modern period, hence are described as participating in an Anglo-Celtic macro-culture. By the same token, the Bretons have been subject to strong Frenchification since the Early Modern period, can be described as participating in a Franco-Celtic macro-culture.
Less common is the assumption of Celticity for European cultures deriving from Continental Celtic roots. These were either Germanised much earlier, before the Early Middle Ages. Celtic origins are many times implied for continental groups such as the Asturians, Portuguese, Northern Italians, Belgians or Austrians; the names of Belgium and the Aquitaine hark back to Gallia Belgica and Gallia Aquitania in turn named for the Belgae and the Aquitani. The Latin name of the Swiss Confederacy, Confoederatio Helvetica, harks back to the Helvetii, the name of Galicia to the Gallaeci and the Auvergne of France to the Averni.'Celt' has been adopted as a label of self-identification by a variety of peoples at different times.'Celticity' can refer to the inferred links between them. During the 19th century, French nationalists gave a privileged significance to their descent from the Gauls; the struggles of Vercingetorix were portrayed as a forerunner of the 19th-century struggles in defence of French nationalism, including the wars of both Napoleons.
Basic French history textbooks emphasised the ways in which Gauls could be seen as an example of cultural assimilation. In the late Middle Ages, some French writers believed that their language was Celtic, rather than Latin. A similar use of Celticity for 19th-century nationalism was made in Switzerland, when the Swiss were seen to originate in the Celtic tribe of the Helvetii, a link still found in the official Latin name of Switzerland, Confœderatio Helvetica, the source of the nation code CH and the name used on postage stamps. Before the advance of Indo-European studies, philologists established that there was a relationship between the Goidelic and Brythonic languages, as well as a relationship between these languages and th