1. Convergence is an important tool to study functions, which means to converge to a point and approach a certain value.

2. The types of convergence are convergence sequence, functional convergence, global convergence and local convergence.

3. A lot of convergence means that the function has a limit.

4. Function convergence criterion: the definition that a function converges to a certain point.

5. For any real number c, there exists a number greater than 0; For any two numbers A and B, it is satisfied that A minus B is greater than 0 and less than C. ..

6. The definition of convergence embodies the essence of mathematical analysis.