1, inf stands for the infimum in mathematics, and its English name is infimum. For the function y=f(x), among all the constants m that make f(x) greater than or equal to m, we call the maximum value max(M) of m (that is, the minimum value of function y=f(x)) as the lower sure bound of function y=f(x).

2. Lower supremum: If there is a maximum lower bound among all these lower bounds, it is called the lower supremum of m.. "Lower supremum" is a basic concept in mathematical analysis, which is defined on the basis of "lower bound". Given a set of numbers e, we call the maximum lower bound of e the lower supremum of e, and we call it infE. Obviously, every element in E is greater than or equal to infE.