terence calls dion Your Highness when he's trying to warn him something's up and to be ready (heading into the tent with that missive from the Emperor that he's clearly already read) or suggest that dion is being reckless ("will you engage him personally...?")

My Prince is for great affection and trust (so... general every day use)

'Dion' ... that's not for us and we should be glad we heard it even once