A governor is, in most cases, a public official with the power to govern the executive branch of a non-sovereign or sub-national level of government, ranking under the head of state. In federations, governor may be the title of the politician who governs a constituent state and may be either appointed or elected. The power of the individual governor can vary dramatically between political systems, with some governors having only nominal, largely ceremonial power, while others have complete power over the entire government.