The Old Polish language (Polish: język staropolski, staropolszczyzna) was a period in the history of the Polish language between the 10th and the 16th centuries. It was followed by the Middle Polish language. The sources for the study of the Old Polish language are the data of the comparative-historical grammar of Slavic languages, the material of Polish dialects, several Latin manuscripts with Polish glosses, as well as – most importantly – monuments written in Old Polish: the Holy Cross Sermons (Polish: Kazania świętokrzyskie), the Florian Psalter (Psałterz floriański), Bogurodzica (Bogurodzica), the Sharoshpatak Bible (Biblia szaroszpatacka or Biblia królowej Zofii) and some others. The Old Polish language was spoken mainly on the territory of modern Poland. It was the main vernacular of medieval Polish states under the Piasts and early Jagiellons, although it was not the state language (that being Latin). Source: Wikipedia (en)