If you’ve worked in or studied UI design – or, if you’re a bit longer in the tooth like me, Human Computer Interaction – ‘Affordance’ is a term that you’re probably quite familiar with. Wikipedia gives the basic definition as :
An affordance is a quality of an object, or an environment, which allows an individual to perform an action. For example, a knob affords twisting, and perhaps pushing, while a cord affords pulling.
If you’ve done the HCI/UI thang though, what you’re probably more familiar with perceived affordance as defined by Don Norman in The Design Of Everyday Things, which is a much more context dependent kind of a concept.