As a method, function is one of the basic tools to describe and analyze phenomena in mathematics. Many problems in mathematics can be described and solved by functions. For example, taking derivative and integral in calculus is to study the change of curve and the calculation of area by using the concept and properties of function. In mathematical analysis, algebra, geometry and other disciplines, function is also an important means to solve problems.

As a tool, function is a basic expression in mathematics. Many concepts and methods in mathematics are expressed by functions, such as polynomials, trigonometric functions, exponential functions and logarithmic functions. In addition, functions are the basis of other tools in mathematics, such as vectors, matrices and differential equations, which can be expressed and solved through the concepts and properties of functions. So function is an indispensable part of mathematics.