A "follis" is a type of ancient Roman coin made primarily of bronze. It was introduced during the reign of Emperor Diocletian in the late 3rd century AD as part of a currency reform. The follis typically featured a portrait of the emperor on one side and various symbols or deities on the other, reflecting the political and cultural values of the time. The follis was used in everyday transactions and was an important part of the Roman economy. Over time, its value and composition changed, especially during the decline of the Roman Empire. The coin remains a significant artifact for historians studying Roman history and economics.