(phonology) The replacement or merger of the Polish language's series of retroflex fricatives and affricates /ʂ, ʐ, t͡ʂ, d͡ʐ/ (written sz, ż, cz, dż) into the alveolar series /s, z, t͡s, d͡z/ (written s, z, c, dz), present in Masovian and other dialects.