To start using Common in game (after using some other language, since Common is your selected language by default), type -- console command for Mith's Virtual Console.
Common is the common language of Faerûn. Almost every sentient civilized being speaks a smattering of it and most are fluent. While most cannot read or write the language, generally, the people of Faerûn will be able to converse with each other in this language.
It is also known as the Trader's Tongue, or, by more dark groups, as the Slave's Tongue.
On Arelith the Drow sometimes put in "Drow words" in their sentences, even when they just speak Common, to represent their accent.
On Arelith this language is known by: