微分方程（这里指的是常微分方程）指含有一次、二次、乃至高次微分未知数的方程。是解决偏微分方程、数理方程的基础。有许多特殊函数，都是为了无法得出多项函数或超越函数型式的解析解的微分方程而定义出来。这些特殊函数之所以重要，是因为它们描述了自然界中的某些现象，例如，电子的活动、鼓皮的振动、钟摆的摆动等等。-Differential equations (in this case is the ordinary differential equation) means containing one, two, and even high-differential equations unknowns. Is to solve the partial differential equations, mathematical equations based. There are many special functions, are not drawn to a number of functions or functions beyond the type of analytical solution of differential equations which define them. These special functions are important because they describe the nature of certain phenomena, for example, electronic activities, drum skin vibrations, pendulum swing, and so on