“The ancient dukedom held vast lands and had dominion over multiple baronial territories.”
“Queen Elizabeth II bestowed a dukedom upon her grandson, granting him the noble title of Duke.”
“With the support of the King of Naples, his brother raised an army and expelled him from the dukedom with his daughter.”
duchy
A dominion or region ruled by a duke or duchess. (A grand duchy may be a self-governing state. A simple duchy tends to be a part of a larger kingdom or empire.)
“Second to Adrian Maguire in the pecking order at David Nicholson's, Johnson has in place an agreement to ride as number one for Henry Daly when not obliged to his Dukeship.”