微分方程，有时简称为方程，未知函数是一元函数的微分方程称作常微分方程，未知数是多元函数的微分方程称作偏微分方程。微分方程中出现的未知函数最高阶导数的阶数，称为微分方程的阶。-Differential equations, sometimes referred to as the equation, the unknown function is called Differential DOLLAR FUNCTION ordinary differential equations, differential equations is unknown multivariate function is called partial differential equations. Order differential equations appearing in the highest order derivative of the unknown function, called differential equations.