About Polish
Polish is a West Slavic language and the official language of Poland. Its written standard is the Polish alphabet which corresponds basically to the Latin alphabet with a few additions. Polish-speakers use the language in a uniform manner throughout most of Poland.

The Polish language became far more homogeneous in the second half of the 20th century, in part due to the mass-migration of several million Polish citizens from the eastern to the western part of the country after the Soviet annexation of the Kresy in 1939. This tendency toward a homogeneity also stems from the vertically integrated nature of the authoritarian People's Republic of Poland.

source: Wikipedia