A duke is a nobleman with the highest rank below royalty. In countries with kings and queens, dukes traditionally ruled large territories called duchies and held significant power and wealth. The title passes down through families, so a duke's oldest son often becomes the next duke. (If a daughter inherits a dukedom, she is called a duchess rather than a duke).

Dukes historically led armies and governed regions on behalf of the monarch. In medieval Europe, a duke might control vast lands, collect taxes, maintain castles, and command soldiers. Today, while some European countries still have dukes, the title is mostly ceremonial rather than powerful.

In some places, “duke” also means a fist. When someone says “put up your dukes,” they mean to raise your fists as if ready to fight, though the phrase is usually used playfully rather than seriously.

The feminine form of duke is duchess. Famous dukes include the Duke of Wellington, who defeated Napoleon at Waterloo, and the Duke of Normandy, who conquered England in 1066. You might also know Duke Ellington, the legendary jazz musician, though in his case “Duke” was a nickname rather than a noble title.