Let's chat about languages real quick! OSE has a
decent list of languages you can roll for (or choose), and there are a few regional languages. There is the common tongue- Westerling as it is known- as well as Gasquen, Kirkut, and High Boros. Gasquen is used to the south and the east, and is the language of the Foere nobility. Kirkut is used to the west in Reme to the west. High Boros is an ancient tongue that isn't really used today, but is marked in many ruins.
Each character can start with Common and their Racial or Regional language, and can choose to learn racial/regional/alignment languages with their Int bonus languages. Alignment languages are only for Lawful or Chaotic, and are a rough version of Celestial and Infernal.
I'm not here for a full simulation of language dynamics, but they will sometimes come into play. Monsters may not speak Westerling, which would make diplomacy difficult or impossible. Likewise, it might be useful to know that the thirty-eyed creature of blazing flame and confusing rings is speaking Celestial, and is actually an angel trying to help.