“Conlangs” (constructed languages) are hardly new: Esperanto and Volapük were created in the 19th century; Tolkien claimed he wrote his Middle Earth books so that someone would speak the Elvish tongues he invented; Klingon was completed in the 1980s. But over the past 30 years, conlangs have exploded (aided greatly by the Internet connecting the nerds who do the constructing). Some of these languages are being used in neurolinguistic research, and one has been developed as a useful lingua franca for Slavs. – Slate