"Basic Theory of Fractional Differential Equations" is a contemporary collection of 16 articles that explores modern methods and applications of FDEs. It covers the extended Jacobi elliptic function expansion method, numerical approximation techniques like -step continuous BDFs for FIVPs, stability theories, and various fractional derivatives. The book finds applications in diverse fields, making it a valuable tool for solving real-world problems in physics, engineering, finance, and biology.