King-emperor
A king-emperor or queen-empress is a sovereign ruler who is simultaneously a king or queen of one polity and emperor or empress of another. This dual title usually results from merger of one royal and one imperial crown (ruling office), but recognises the two polities as politically distinct and their supreme magistracies, i. e., political offices, as different in form. It also denotes the imperial status of a king who holds it by virtue of acquisition of an empire or vice versa.
The dual title may signify that the sovereign holds two political offices that differ in form, one in each polity subject to him, but it also may have been instituted merely to augment the prestige of the sovereign. Both instances, however, signify that the union of the two supreme political magistracies into one officeholder, i. e., sovereign, is not by virtue of annexation, in which one polity was amalgamated into another, yet rather of unification and almost equal status, though in the instance of the British monarchy the suggestion that the office of emperor was superior to that of king was avoided by instituting the title "king-emperor" ("queen-empress") instead of "emperor-king" ("empress-queen").