The following is an introduction to the limit:

For the unknown quantity under investigation, first try to correctly conceive another variable related to its change, and confirm that the trend result of the' influence' of this variable through the infinite change process is very accurate and approximately equal to the unknown quantity sought; The result of the unknown quantity under investigation can be calculated by the limit principle.

The idea of limit is the basic idea of calculus and a series of important concepts in mathematical analysis, such as continuity of function, derivative (maximum value is 0), definite integral and so on. These are all defined by the way of limit.

If you want to ask, "What is the theme of mathematical analysis?" Then it can be simply said: "Mathematical analysis is a subject that studies functions with limit thought, and the error of calculation results is too small to imagine and can be ignored.

Refer to Baidu Encyclopedia-Limits for the above information.