Dukedom

Noun

 * 1) a region ruled by a duke or duchess; a duchy
 * 2) the rank or title of a duke

Thesaurus
ally, archduchy, archdukedom, baronetcy, barony, body politic, buffer state, captive nation, chieftaincy, chieftainry, city-state, colony, commonweal, commonwealth, country, county, domain, dominion, duchy, earldom, empery, empire, free city, grand duchy, kingdom, kingship, knight-errantship, knighthood, ladyship, land, lordship, mandant, mandate, mandated territory, mandatee, mandatory, marquisate, nation, nationality, pashadom, polis, polity, possession, power, princedom, princeship, principality, principate, protectorate, province, puppet government, puppet regime, queenship, realm, republic, satellite, seignioralty, seigniory, seneschalty, settlement, sovereign nation, state, sultanate, superpower, territory, toparchia, toparchy, viscountcy, viscountship, viscounty

Etymology

 * duke + -dom