A term from ecological psychology, used to understand things by what they “afford” a user in contrast to understanding a thing based upon its explicit purpose.
A glass bottle’s purpose is holding liquids, but one can discover that it affords one many ways to make sounds from tapping to blowing across the mouth. By privileging things affordances we open ourselves to a vast space of unintended possibilities which are critical to innovation. Much non-human innovation emerges via unintended affordances (see Exaptation).
What is critical is thinking about things not as what a thing “is” but what it can do. This is situational, relational and emergent. Because of this relation and emergent logic there is no end to the number of affordances.
A leaf's affordances include a shade, sustenance or, materials for a roof.