Wiktionary
n. A potential action that is made possible by a given object or environment; ''especially'', one that is made easily discoverable.
Wikipedia
An affordance is the possibility of an action on an object or environment.
Additional meanings have developed, largely a result of misinterpretations. The original definition in psychology includes all actions that are physically possible. When the concept was applied to design, it started also referring to only those action possibilities which one is aware of.
The word is used in a variety of fields: perceptual psychology, cognitive psychology, environmental psychology, industrial design, human–computer interaction (HCI), interaction design, communication studies, instructional design, science, technology and society (STS), and artificial intelligence.
Usage examples of "affordance".
However, there's something about a hammer that cries out for nail-bashing, it has affordances that tilt its holder towards swinging it.
The affordance of the Internet is to move bits at very high speed around the world at little-to-no cost.