Answer:
A duke is the member of nobility that ranks just below the monarch. A duke is a ruler of a 'duchy' (county, territory or domain). It's also tradition for men of the royal family to get a new title when they marry - often taking on duke status.
A duchess is the wife or widow of a duke, or a woman who equal holds the rank of duke in her own right. Baron is a rank of nobility or title of honor, often hereditary. The female equivalent is baroness.
A baron is a member of the lowest order of the British nobility. A baron is a nobleman — a member of the aristocracy. Barons are also important, powerful businessmen with huge influence over their industries.