The Celtic languages are a group of related languages descended from Proto-Celtic. They form a branch of the Indo-European language family. The term "Celtic" was first used to describe this language group by Edward Lhuyd in 1707, following Paul-Yves Pezron, who made the explicit link between the Celts described by classical writers and the Welsh and Breton languages.
The second of the four Botorrita plaques. The third plaque is the longest text discovered in any ancient Celtic language. However, this plaque is inscribed in Latin script.
The Indo-European languages are a language family native to the overwhelming majority of Europe, the Iranian plateau, and the northern Indian subcontinent. Some European languages of this family—English, French, Portuguese, Russian, Dutch, and Spanish—have expanded through colonialism in the modern period and are now spoken across several continents. The Indo-European family is divided into several branches or sub-families, of which there are eight groups with languages still alive today: Albanian, Armenian, Balto-Slavic, Celtic, Germanic, Hellenic, Indo-Iranian, and Italic; another nine subdivisions are now extinct.
Franz Bopp was a pioneer in the field of comparative linguistic studies.
Indo-European language family tree based on "Ancestry-constrained phylogenetic analysis of Indo-European languages" by Chang et al.
Scheme of Indo-European language dispersals from c. 4000 to 1000 BCE according to the widely held Kurgan hypothesis. – Center: Steppe cultures 1 (black): Anatolian languages (archaic PIE) 2 (black): Afanasievo culture (early PIE) 3 (black) Yamnaya culture expansion (Pontic-Caspian steppe, Danube Valley) (late PIE) 4A (black): Western Corded Ware 4B-C (blue & dark blue): Bell Beaker; adopted by Indo-European speakers 5A-B (red): Eastern Corded ware