Draconic

The language of Dragons is both ancient and powerful. It is fiendishly difficult to pronounce, but the syntax of the language seems to have magic woven into its structure, and most arcane spells with a verbal component feature draconic incantations. This language is studied primarily by scholars and wizards. Few dare to try speaking it to dragons, as a poorly understood word could easily be fatal in such a situation.
Wizards can usually understand at least a bit of draconic, even if they can't speak it.