Textbook of Usability

An affordance is a relationship between the properties of an object and the capabilities of the agent using it, determining how the object could be used. The term was coined by the perceptual psychologist James J. Gibson (1979) and introduced to design by Don Norman in The Design of Everyday Things (1988).

A flat plate on a door affords pushing. A handle affords pulling. A slider affords dragging. A button affords pressing. These are not properties of the object alone, nor of the user alone — they emerge from the relationship.

Norman later distinguished:

• Real affordances: physical properties that genuinely enable an action
• Perceived affordances (later called signifiers): visual cues that suggest how an object can be used

A glass door without a visible handle has the real affordance of pushing (you can push it) but no perceived affordance — the user cannot tell how to interact with it. This mismatch is the source of countless "Norman doors" (doors people push when they should pull).

In software, affordances are entirely perceived — pixels cannot truly be grasped. A button that looks raised, a link that looks underlined, a field that looks editable — all use visual conventions to suggest action possibilities. Flat design movements of the 2010s reduced these visual cues in pursuit of simplicity, sometimes at the cost of discoverability.

The concept of affordance is central to understanding why some interfaces feel intuitive while others require explicit instruction.