When you slice off and eat half a pizza, then slice off and eat half of the remaining half, then slice off and eat half of the remaining portion, and continue slicing and eating 'till infinity arrives, we say the amount of pizza remaining at any time decreases according to the rules of a first order process. Your acid reflux will also follow a first order process increasing gurgitation in response to the disappearing pizza. Pizza reflux is a 'fast' first order reaching finality in minutes. At a different pace, radioactive plutonium-239 decays with a half life of 24,000 years, losing its potency at an incredibly 'slow' rate.
Outside, pollutants in our rivers often decay by first order rules extending over days and sometimes weeks. Dump waste water in the river at point A. By the time it reaches point B indigenous bacteria will consume it as food, maybe not by halves, but as a first order process nonetheless. Unfortunately, feeding bacteria also remove dissolved oxygen, again as a first order process, suffocating innocent aquatic life in the way. (Aquatic life can also suffocate rather suddenly; we call that a 'delta function'). Rivers can get reflux too.
Folks like me spend our working days (and sleepless nights) trying to understand and quantify the multitude of first order reactions at play in the river at any place, at all times. For the health of the river we must calculate the precise amount of waste water control needed to neutralize any reflux, and regulate unruly first order processes to within very tight limits, for the foreseeable future. No runaway first order processes allowed, in my town!
Let's hear it for the Water Scientist.