In Polish linguistic tradition there are seven general dialectal groups of the Polish language, each primarily associated with a certain geographical region. The dialects (dialekt in Polish) are often further subdivided into subdialectal groups called gwara or region.
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 east was annexed by the Soviet Union in the aftermath of World War II.
The regional differences correspond mainly to old ethnic or tribal divisions from around a thousand years ago; the most significant of these in terms of numbers of speakers are Greater Polish (spoken in the west), Lesser Polish (spoken in the south and southeast), Mazovian (Mazur) spoken throughout the central and eastern parts of the country, and Silesian language in the southwest. Mazovian shares some features with the Kashubian language.