The official language of the Czech Republic, the Czech language is spoken by about 12.5 million people. Historically, Czech is considered the language of the Silesia, Moravia, and Bohemia regions - which once comprised the western and central territories of the former Czechoslovakia - and which today constitute the Czech Republic. A large number of Czech speakers live in the United States (some 1.5 million) and Canada (about 30,000). Czech is a Slavic language which belongs to the group of Western Slavic languages which includes Slovak and Polish. Both the Czech and Slovak languages can be traced to "Middle Czech," which was used in 15th and 16th centuries, and going farther back, to "Old Czech," which dates to the 11th century. There is a notably strong tradition of translating all varieties of texts into both Czech and Slovak. In the former Czechoslovakia, on average, some 650 literary works, 200 films (either subtitled or over-dubbed), and as many as 150 plays were translated each year.