Common

The common language was derived from numerous sources and has thousands of lingual influences; ciphers that the Stoneborn races used to speak without their draconic masters catching wind of their machinations and elements of planar languages, particularly Sylvan, Primordial, Celestial, Infernal.
While regional dialects and colloquialism do exist throughout the lands, its is (appropriately) the most commonly spoken and known language to the creatures of Agora. The only communities with lesser practice or knowledge are the Giantkin who live high in the mountains, and the underdark societies that fester beneath even dwarvish strongholds.