From Longman Dictionary of Contemporary Englishdukeduke /djuːk $ duːk/ noun [countable] PGOa man with the highest social rank outside the royal family → duchess the Duke of Norfolk
Examples from the Corpus
duke• But his heir, the present duke, no longer holds pole position.• The king gave the duke the rights to more than 1,000 hectares of forested land near the battlefield.• It followed that Northumberland's men were in a sense Gloucester's men, even though the duke could not retain them directly.• Albeit for different reasons, Boris Yeltsin knows what the duke meant.• The duke therefore had to be satisfied with rather less permanent methods of limiting the Woodvilles' power.• There was a particularly promising yarn about a young duke, and Tavett liked a high count of dukes in the column.Origin duke (1100-1200) Old French duc, from Latin dux “leader”, from ducere “to lead” 