I’m sure several languages were spoken given the presence of so many different cultures, but what was the official language of the Kingdom of Jerusalem?
What language was used for state documents?
For trade?
Diplomacy?
I believe the lingua franca was french, given the large number of crusaders of french origin.
I would suspect the state documents were written in latin. That would have been the norm at this time.
As for diplomacy, I know that a number of high-ranked people did speak arabic. I wouldn’t know how widespread it was, though.
I found the following cite (in french) :
“Le latin est la langue officielle sous Guy et Amaury de Lusignan avant d’être remplacé par le français mais la fin de la dynastie verra le retour de l’emploi de la langue grecque.”
Roughly :
“Latin is the official language under Guy and Amaury of Lusignan, before being replaced by french, and towards the end of the dinasty, by greek”.
Guy de usignan was the 10th king of Jerusalem, and the last one actually holding the city (his successors will reign on Acre and Cyprus), so it doesn’t exactly answer the question for the early part of the history of the kingdom.
I found some other cites that let me think that french was indeed the lingua franca in the kingdom. For instance one about the waloon influence in the form of french spoken in the kingdom, or another explaining why french is currently the official language of the patriarchate of Jerusalem.