This book covers the necessary aspects of mathematics for graduate students in physics and engineering. Advanced undergraduate students and researchers who intend to enter the field of theoretical physics can also pick up this book. The first eight chapters include variational method, Hilbert space and operators, ordinary linear differential equations, Bessel functions, Dirac delta function, the Green’s function in mathematical physics, norm, integral equations. Beside these traditional contents, the last two chapters introduce some recent achievements of scientific research while presenting their mathematical background. Like the basis of number theory and its application in physics, material science and other scientific fields, the fundamental equations in spaces with arbitrary dimensions, not limited to Euclid space; Pseudo spherical coordinates. Plain terminologies were used to present the concept of metric, as well as new and interesting work on the Klein-Gorden equation and Maxwell equation.