There is no common language. The predominate language(s) spoken by each race is specified under the respective Races
. This is only a guideline though, because some groups in a region may have spent so much time under the yoke of another, that they may have been forced to adopt the language of their overlords. If this is done long enough, perhaps as little as three generations, there is a good chance that a racial group may have forgotten or given up their ancestral language entirely. A good example of this are the minotaurs.