This book is mainly about four functions denoted by r, R, S, and 2 F 0 . The first is the gamma function, Euler's extension of the factorial function 11! to nonintegral values of 11. The other three are hypergeometric functions and embrace as special cases the functions named after Bessel, Hankel, Legendre, Gauss, Kummer, Whittaker, Jacobi, Chebyshev, Gegenbauer, Laguerre, Hermite, and others. The R function unites Gauss's hypergeometric function with the elliptic integrals and the first Appell function.