Before we discuss the nature of a "fast" timescale, we first need to remark that there is a distinct difference between the way the non-observable reaction evolves as a slow/fast system and the way the indicator reaction evolves as a slow/fast system. To illustrate this difference, let us first remind ourselves of two important features of Tikhonov/Fenichel theory for twodimensional, autonomous dynamical systems. First, let " " be a very small parameter (i.e., 1). Next, suppose our "generic" dynamical system scales (over some timescale) as