Common

Common was the trade language of Faerûn. Almost every sentient civilized being spoke a smattering of it, and most were fluent. While most could not read or write the language, generally, the people of Faerûn were able to converse with each other in this language.

Dialects
Dialects varied from region to region, but generally, communication was possible. Calant was a melodious dialect spoken on the Sword Coast, while Kouroo was a Chultan variant, and Skaevrym was spoken in Sossal.

In other realms, "Common" could be a different form altogether; these were not in fact dialects but different languages. An example was in the Underdark, as the residents there spoke what was known as Undercommon. Inhabitants of different planes also speak different forms of "Common".

Limitations and Advantages
The obvious advantage to Common was that practically every sentient creature could speak it. Even in remote areas of Faerûn like Murghôm, Samarach, and the Great Glacier, the inhabitants could speak at least enough of it to make themselves understood with a little creative pantomiming. Admittedly regional accents had a tendency to confuse the issue; natives of distant areas sometimes regarded each others' accents as strange or silly, but they could still understand each other.

However, it also had its disadvantages; not every concept could be easily related to others. Nuances of speech, names, and phrases could be expressed easier in older languages such as Illuskan and Dwarven.

History and Alphabet
According to Faerûnian linguists, Common developed directly from Thorass, or "Old Common", which was itself a pidgin variant of the Jhaamdathan language ("Old Chondathan") and Alzhedo. Among living languages, Common was most closely related to Chondathan.

Common used the Thorass alphabet.