Common Tongue is a universal language spoken by the inhabitants of Erudite. While many civilizations prefer to speak their native language, Common Tongue is considered the trading language of Erudite. Therefore, most of its syntax and grammar are focused on bartering and trading terms.
The Great Library, the catalogue of information on every bit of lore about Erudite and the nearby planes, are all written in Common Tongue, because other languages will change while Common Tongue remains the same.
The language is notably more complex than most languages because a wide variety of different sentence structures are needed to get across the meaning of a term which is usually not possible in local languages.
Unlike many languages which quickly evolve over thousands of years, Common Tongue has remained a rather stagnant language, being designed that way so that it can remain consistent over the years to prevent possible misunderstandings. As a result, Common Tongue has yet to become the one, single language of Erudite because standard trading procedure does not allow for new words to be added to the language.
Common Tongue was created during the formations of the first civilizations. It was based on the language of the Gods - therefore it bears a resemblance to the language known as English. Since then, it has been the common practice of many civilizations to learn both their native language and Common Tongue. The former being used among themselves, and the latter being used to communicate with other civilizations.