Frisian Language, language of the historical Frisian people, now an official language in the Dutch province of Friesland, with dialects still spoken on the Frisian Islands, and in a few German villages. Frisian, most closely related to English, belongs to the Anglo-Frisian group in the western branch of the Germanic languages. Similar Frisian and English words include boi (boy), tolve (twelve), and hy (he). Frisian was once the prominent tongue along the North Sea coast and on nearby islands, from the present Dutch-Belgian border to the modern German-Danish border. Since the 16th century, Frisian has gradually been replaced by Dutch and Low German, but it was revived in the 20th century. See also Frisia; Frisian Literature.