1. Unbounded is a range definition, which means that there is no boundary in the range, and it is not necessarily required to be close to unbounded. This definition means that for any g >；; 0, at least one n exists, so that xn >；; G, that is, in an infinite number greater than n, as long as at least one of them is greater than g, it is not necessary to be greater than all.

2. Infinity is a limit concept, an approximation process, and the limit is infinite. The definition of infinity is for any g >. 0, with n>n, so that any xn >；; g .