I removed this from http://en.wikipedia.org/wiki/Pierogi, but it may very well be useful here at Wiktionary:
In Polish, pierogi is plural, pieróg being singular. Other Slavic languages follow the same scheme. In Russian and Ukrainian, the singular form of words derived from "pir"—the Russian pirog (пирог, pl. пироги, stress on the last syllable) or the Ukrainian pyrih (пиріг, pl. пироги, stress on the last syllable)—refers to a different type of food, such as pies or pirozhki.
184.108.40.206 19:46, 7 July 2009 (UTC)
Polish pierogi are not equal to Russian/Ukrainian пироги (Russian sg.: пирог, Ukrainian sg.: пиріг)
Polish dish called pierogi is identical to the Russian pelmeni or one Slavic type of dumplings (another one being vareniki (ru)/varenyky (uk). The Russian/Ukrainian пироги is plural for пирог (ru), пиріг (uk), which is pie, not dumplings or pirozhki Anatoli 02:13, 5 August 2009 (UTC)