From Longman Dictionary of Contemporary EnglishHighnessHigh‧ness /ˈhaɪnəs/ noun [countable] → Your/Her/His Highness
Examples from the Corpus
Highness• Her Royal Highness went round the room meeting many of those who had supported this Gala evening.• Your Royal Highnesses, Your Excellencies, distinguished cabinet ministers and ambassadors, ladies and gentlemen.• No, Your Highness, you are, of course, welcome to stay.• Besides, I don't want anything from you, Your Highness. 