A quantity is said to be constant if it remains constant during a certain movement of things.
On the contrary, it is called a variable and is widely used in life.
Usage of constants and variables: The process of mathematical research object from constants to variables shows that people's research on the quantitative relationship of things has changed from a static and isolated point of view to a moving and related point of view.
This change of thinking mode reflects that dialectics has entered mathematics.
As Engels said, the turning point in mathematics is Descartes' variables, and variable mathematics is essentially nothing more than the application of dialectics in mathematics.