殿下

noun

Your/His/Her Highness (address for crown princes, princes, or princesses)

Historically used for addressing members of the imperial family below the emperor (e.g., crown princes, princes, princesses). In modern contexts, it is primarily used in formal diplomatic language or historical dramas to address foreign royalty, equivalent to 'Your Highness'. The character '殿' originally means 'palace hall', implying the residence of a royal person.