highnesses
n. 殿下,閣下(用作對皇室成員的尊稱)( highness的名詞複數 )
Expressions such as 'Your Highness' or 'His Highness' are used to address or refer to a member of the royal family other than a king or queen.
That would be best, Your Highness...
那樣最好了,殿下。
Her Royal Highness the Duchess of Kent opened an art exhibition recently.
肯特公爵夫人殿下最近為一個藝術展覽揭幕。