Definition: The term "dilogarithm" is a mathematical function in complex analysis and number theory, specifically used in the study of the logarithmic derivative. It was introduced by the German mathematician August Ferdinand Liouville around 1860, who called it a "logarithm to the second power." The dilogarithm is closely related to the concept of the digamma function, which is used in mathematical analysis and complex analysis to study the behavior of certain functions.