Polish began to emerge as a distinct language around the 10th century, the process largely triggered by the establishment and development of the Polish state.
Mieszko I, ruler of the Polans tribe from the Greater Poland region, united a few culturally and linguistically related tribes from the basins of the Vistula and Oder before eventually accepting baptism in 966.
It is also spoken as a second language in northern Czech Republic and Slovakia, Hungary, western parts of Belarus and Ukraine, and central-western Lithuania.
Because of the emigration from Poland during different time periods, most notably after World War II, millions of Polish speakers can be found in countries such as Israel, Australia, Argentina, Brazil, Canada, the United Kingdom, Ireland, and the United States.
"It is worth mentioning," writes Tomasz Kamusella, "that Polish is the oldest, non-ecclesiastical, written Slavic language with a continuous tradition of literacy and official use, which has lasted unbroken from the 16th century to this day." The precursor to modern Polish is the Old Polish language.
Some Poles remained in the previously Polish-ruled territories in the east that were annexed by the USSR, resulting in the present-day Polish-speaking minorities in Lithuania, Belarus, and Ukraine, although many Poles were expelled or emigrated from those areas to areas within Poland's new borders.