K-convex functions, first introduced by Scarf, are a special weakening of the concept of convex function which is crucial in the proof of the optimality of the ( s , S ) {\displaystyle (s,S)} policy in inventory control theory. The policy is characterized by two numbers s and S, S ≥ s {\displaystyle S\geq s} , such that when the inventory level falls below level s, an order is issued for a quantity that brings the inventory up to level S, and nothing is ordered otherwise. Gallego and Sethi have generalized the concept of K-convexity to higher dimensional Euclidean spaces.