1. Plural of highness; a title of respect used to address or refer to royalty, especially princes, princesses, and other members of royal families.
Usage: Formal and ceremonial usage; Often capitalized when used as a direct form of address
2. The quality or state of being high in position, rank, or dignity.
Usage: Archaic or literary usage

Examples

• Their Highnesses the Prince and Princess attended the state dinner.
• The protocol required all guests to address the royal family as 'Your Highnesses.'
• Several highnesses from European royal families gathered for the conference.
• The ceremony honored the highnesses with a formal reception.
• Your Highnesses are most welcome to our kingdom.