Highness is a formal
style used to address (in
second person) or refer to (in
third person) certain members of a
reigning or formerly reigning
dynasty. It is typically used with a
possessive adjective: "His Highness", "Their Highnesses", etc. Although often combined with other adjectives
of honour indicating rank, such as "Imperial", "Royal" or "Serene", it may be used alone.