A monarch is the sovereign head of state, officially outranking all other individuals in the realm. A monarch may exercise the most and highest authority in the state or others may wield that power on behalf of the monarch. Typically a monarch either personally inherits the lawful right to exercise the state's sovereign rights (often referred to as the throne or the crown) or is selected by an established process from a family or cohort eligible to provide the nation's monarch. Alternatively, an individual may become monarch by conquest, acclamation or a combination of means. A monarch usually reigns for life or until abdication. Monarchs' actual powers vary from one monarchy to another and in different eras; on one extreme, they may be autocrats (absolute monarchy) wielding genuine sovereignty; on the other they may be ceremonial heads of state who exercise little or no power or only reserve powers, with actual authority vested in a parliament or other body (constitutional monarchy).