What is the Difference Between Duke and Earl?

The main differences between the titles Duke and Earl are in their rank and the size of the land they hold. Both titles are part of the British peerage system, which ranks individuals based on their social status and political influence. The ranks, from highest to lowest, are: Duke, Marquess, Earl, Viscount, and Baron.

Duke: The highest rank in the peerage system, a duke holds the largest land holdings, known as duchies. Dukes were originally sovereign rulers, but the title was incorporated into the peerage system in 1337. The title is derived from the Latin term "dux," which means leader. Dukes are a dying breed, as the title can only pass down the male line.
Earl: The third rank in the peerage system, an earl stands above the ranks of Viscount and Baron but below Duke and Marquess. An earl holds larger land holdings than a baron, but smaller than a duke. The title "Earl" originates from the Old English word "eorl," which means "noble" or "stranger". There are currently 191 Earls and four Countesses in the United Kingdom.

In summary, while both titles indicate a high social status and political influence, a Duke holds the highest rank in the peerage system, with the largest land holdings, while an Earl holds a lower rank with smaller land holdings.