A bounded below set is a ARA\subseteq\mathbb R for which there exists mRm\in\mathbb R such that mxm\le x for every xAx\in A; such an mm is called a lower bound of AA.

Examples
  • A=(0,1)A=(0,1) is bounded below (for example, by m=0m=0).
  • A=RA=\mathbb R is not bounded below.
Remarks

This notion uses the and is the basic hypothesis needed to define the . A set can be bounded below without having a .