The first form of this relation allows a simple interpretation: the probability flow is proportional to the spatial gradient of the probability density (i.e., in application to N >> 1 similar and ...The first form of this relation allows a simple interpretation: the probability flow is proportional to the spatial gradient of the probability density (i.e., in application to N >> 1 similar and independent particles, just to the gradient of their concentration n = Nw), with the sign corresponding to the flow from the higher to lower concentrations.