About: Non-European royal and noble ranks

Some titles of nobility outside Europe may be considered as equivalents of Duke. Like other major Western noble titles, Duke is sometimes used to render (translate) certain titles in non-western languages. "Duke" is used even though those titles are generally etymologically and often historically unrelated and thus hard to compare. However, they are considered roughly equivalent, especially in hierarchic aristocracies such as feudal Japan, useful as an indication of relative rank.