positive externality A desirable impact of a transaction between two parties (individuals, business firms, government) upon a third, uninvolved individual or group. Related Related Articles: What Space Travel Brought Back to EarthWhy 12 Bottles of Bordeaux Were on the International Space StationWhat NASA Brings Back To EarthHow the Ever Forward Is Like Her SisterHow Whiskey Made Green Crabs Less Invasive Ann Mills Share This Previous Articleopen corporation Next Articlerecession December 17, 2020