In mathematics, the meaning of c varies with the context and field. C stands for the number of combinations in algebra, which is usually used to represent the number of combinations of r elements among n elements. In geometry, c can be used to represent the coordinates of points or the perimeter of a plane figure, that is, the length of the figure boundary. In complex mathematics, c stands for complex set, including real number and imaginary number. Real number is the number corresponding to the point on the number axis, and imaginary number is the number with negative square or negative root sign. In indefinite integral, c stands for any constant, which is used to represent the special solution of indefinite integral. C has many meanings in mathematics. Only by using it flexibly according to specific situations and fields can we accurately understand its meaning.