Differential equation is a mathematical equation to describe the relationship between a function and its derivative. In the algebraic equation of elementary mathematics, its solution is a constant value. Differential equations can be divided into ordinary differential equations and partial differential equations. It is widely used in chemistry, engineering, economics and population statistics.

Many basic laws of physics or chemistry can be written in the form of differential equations. In biology and economics, differential equations are used as mathematical models of complex systems. The mathematical theory of differential equations first appeared together with the corresponding field of equation science, and the solutions of differential equations can be used in this field. However, sometimes two completely different scientific fields will form the same differential equation. At this time, the mathematical theory corresponding to differential equations can show the consistent principle behind different phenomena.