Classical Nahuatl (also known simply as Aztec or Nahuatl) is any of the variants of Nahuatl spoken in the Valley of Mexico and central Mexico as a lingua franca at the time of the 16th-century Spanish conquest of the Aztec Empire. During the subsequent centuries, it was largely displaced by Spanish and evolved into some of the modern Nahuan languages in use today (other modern dialects descend more directly from other 16th-century variants). Although classified as an extinct language, Classical Nahuatl has survived through a multitude of written sources transcribed by Nahua peoples and Spaniards in the Latin script. Source: Wikipedia (en)