noun
A high-ranking noble title in European and Japanese peerage systems. In Japanese history, it was the highest of the five ranks (五等爵) established in the Meiji era. When referring to British royalty, 'prince' may be used for certain dukes, but the primary equivalent is 'duke'.
See also: 五等爵
彼は公爵の称号を持っている。
He holds the title of duke.
エディンバラ公爵は英国王室の一員です。
The Duke of Edinburgh is a member of the British royal family.