All characters in Crusader Kings III: Royal Court have a specific language. However, your characters are not limited to a single dialect and you can turn them into a multilingual. This is ours Crusader Kings III: Royal Court tutorials to help you learn new languages.
Crusader Kings III: Royal Court Tutorial – How to learn a new language
There are several ways to learn a language in Crusader Kings III: Royal Court campaign. You can simply right click on the character’s portrait and select the Learn Language option. This will then lead to a personal plan with a sequence of events that may succeed or fail over the next few years.
Another option is also available to those who have unlocked the Royal Court (i.e. those with kingdom or empire level titles). Switch to Court Language map mode to check what’s active in neighboring territories. If your ruler does not know Court Languagethey can hire a linguist through a decision.
In the example you see below, Georgia has Greek as the language of the Royal Court. Unfortunately, the king could not speak Greek, which meant he could hire someone to help him. The specified character is given Court Assistant Positiongives a bonus to the power of the Language Learning scheme (although you still need to right-click someone to be able to learn that language).
Note: Designated Court Tutors can right click on children in their domain to ask them to learn a new language. This aids their growth, especially if you are nurturing them to lead a nation in the future.
When you learn a language in Crusader Kings III: Royal Court, you get an opinion bonus from people who speak that language. This can be useful when it comes to diplomatic and personal proposals.
Similarly, it is helpful to know how to say the right words due to random events. There are places where you meet new characters or when vassals pay their respects to a ruler. If the characters don’t understand each other, it can lead to a bit of misunderstanding. For example, vassals may be given a silly nickname (i.e. The Foreigner) if they consider themselves idiots.
https://www.pcinvasion.com/crusader-kings-3-royal-court-learn-language-guide/ Royal Court – How to learn a new language