Vector space, also known as linear space, is the central content and one of the basic concepts of linear algebra. After introducing the concept of vector into analytic geometry, many problems are handled more concisely. On this basis, the concept of vector space associated with domain is further abstracted. For example, the polynomial set of real coefficients forms a vector space after defining appropriate operations, which is convenient for algebraic processing. A set of real functions with one variable also constitutes a vector space after defining appropriate operations. The branch of mathematics that studies this kind of function vector space is called functional analysis.