It refers to the cost or benefit of an activity by an economic agent for which it does not pay a price.
Fr ex: factory produces goods , it releases harmful smokes n polluts our enviroment.
In this case externality implies the negetive effect.
Hope it helped u!!
Endangered Species. An animal or plant species is considered 'endangered' when it is at the risk of becoming extinct from the planet or from a particular region on the planet. Most of these species are considered to be endangered as they are at the risk of becoming extinct with only a few individuals surviving.
Gray matter is what this consists of