In mathematics, the infimum or greatest lower bound of a setA, written as , is the greatest element among all lower bounds of A. Similarly, the supremum or least upper bound of A, written as , is the smallest element among all upper bounds of A.
For example, if A is the set , then and . Infimum and supremum are unique, if they exist. Infimum and supremum are key concepts in the field of mathematical analysis.