It's standard terminology. The point is that the threshold is different depending on whether you are coming from above or below. See here: https://en.m.wikiped

It's standard terminology. The point is that the threshold is different depending on whether you are coming from above or below. See here: https://en.m.wikipedia.org/wiki/Hysteresis#Rate-independent https://en.m.wikipedia.org/wiki/Hysteresis#Rate-independent