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A presidential system, or single executive system, is a form of government in which a head of government, typically with the title of president, leads an executive branch that is separate from the legislative branch in systems that use separation of powers. This head of government is in most cases also the head of state. In a presidential system, the head of government is directly or indirectly elected by a group of citizens and is not responsible to the legislature, and the legislature cannot dismiss the president except in extraordinary cases. A presidential system contrasts with a parliamentary system, where the head of government comes to power by gaining the confidence of an elected legislature.