Before revision: Grand duke is the usual and established, though not literal, translation of these terms in English and Romance languages, which do not normally use separate words for a "prince" who reigns as a monarch (e.g., Albert II, Prince of Monaco) and a "prince" who does not reign, but belongs to a monarch's family (e.g., Prince William, Duke of Cambridge ).
After revision: Grand duke is the usual and established, though not literal, translation of these terms in English and Romance languages, which do not normally use separate words for a "prince" who reigns as a monarch (e.g., Albert II, Prince of Monaco) and a "prince" who does not reign, but belongs to a monarch's family (e.g., Prince George of Wales ).