A useful chromatographic parameter–the column characteristic, [Ggrave]–is defined and derived. It contains all of the dynamic information of interest for chromatography, yet it can be determined from a single-stage experiment. The column characteristic can be employed directly to derive the column transfer function and is related to the Murphree stage efficiency for the chromatographic column operated as a single equilibrium stage. The relationship of the column characteristic to the first normal statistical moment is derived. Application is made to a simple physical situation and results are obtained for both a distributed and a discrete description of the stationary liquid phase. The nature of the discrete approximation is discussed. This paper provides the foundation for two additional papers that explore in detail several aspects of nonequilibrium chromatography.