The Ruthenian language, also called Chancery Slavonic in its written form, was used to write laws alongside Polish, Latin and German, but use varied between regions. From the time of Vytautas, there are fewer remaining documents written in Ruthenian than there are in Latin and German, but later Ruthenian became the main language of documentation and writings, especially in eastern and southern parts of the Duchy. In the 16th century at the time of Polish–Lithuanian Commonwealth, Lithuanian lands became partially polonized over time and started to use the Polish language for writing much more often than the Lithuanian and Ruthenian languages. Polish finally became the official chancellery language of the Commonwealth in 1697.