What is the difference between a duke and a grand duke and arch duke?

Answer 1

A duke is a noble rank in various European countries, typically below a prince but above a marquess. A grand duke is a higher rank than a duke, often ruling over a territory or principality, particularly in countries like Luxembourg or historically in parts of the Holy Roman Empire. An archduke is a title primarily associated with the Habsburg dynasty, indicating a rank above a duke but below a king or emperor, notably used for heirs to the Austro-Hungarian throne.