A monarchy is a form of government in which a person, the monarch, is head of state for life or until abdication. The political legitimacy and authority of the monarch may vary from restricted and largely symbolic (constitutional monarchy), to fully autocratic (absolute monarchy), and can expand across the domains of the executive, legislative, and judicial. A monarchy can be a polity through unity, personal union, vassalage or federation, and monarchs can carry various titles such as emperor, king, queen, raja, khan, caliph, tsar, sultan, shah, or pharaoh.