Marai: The Long Dark
There is a ‘common’ human language, but each has a different dialect, akin to say British, American Northeast, American South, and Jamaican – the language is known as Shadree, and has evolved considerably from what is now known as Old Tongue (Old Shadree). All speakers of Shadree can understand another speaker, albeit with some difficulty. For example, the Shen and the Naktu each claim the other speaks as if they had a mouth full of sand. As far as a trade language, though, there really isn’t one.
There isn’t a Draconic language, as there are only four dragons and they speak Godtongue. Godtongue cannot be learned by most mortals. Magic is less a language, and more a channeling of power though the use of an extremely simplified version of Godtongue; the verbal part of magic calls the energy, the somatic acts as a rod, and any components act as a focus. There is no actual language, as most of it is situational, rather than specific. To give you an idea of the complexity of Godtongue, imagine hearing the first word your daughter spoke, and it being understood to be the entire collection of writings of Shakespeare.
There are two Elven languages – the first is the language spoken in the presence of other races, and there is a dialect for each of the sub-races and is also spoken by the Fey. The second language, known as Maraithel, is a language spoken only between Elves. It is considered to be a mortal sin to teach the language to non-Elves, and any other race found using Maraithel for any reason are immediately seized and interrogated, and sometimes killed. It is said that Maraithel was a gift from Sol Linaru to the Children of Ilsidelius, so they could solemnly perform their duties as stewards of Marai. It is a language steeped in tradition, and will often be used in intimate settings.