A sich (Ukrainian: Січ) is the administrative and military centre for Cossacks and especially the Zaporizhian Cossacks. It is derived from the Ukrainian word siktý, "to chop", meaning to clear a forest for an encampment, or to build a fortification with the trees that have been chopped down.
The Zaporizhian Sich was the fortified capital of the Zaporizhian Cossacks in the 16th to 18th century area of Ukraine and was located on the Dnieper River. The Sich Rada was the highest branch of government in the Zaporizhian Host or army of the Zaporizhian Cossacks. The Danubian Sich was the fortified settlement of the Zaporozhian Cossacks who later settled in the Danube Delta.