Affordance
The perceivable property of an element that indicates how it can be used — the shading that says “press me,” the handle that says “drag me.”
Example usage
“The card is clickable but nothing affords it — no cursor change, no elevation, no hover response.”
Editor’s note
Strictly, an affordance is the action possibility itself; the visible hint is a signifier — a distinction Don Norman spent a career defending and designers ignore daily. The working rule survives the pedantry: every interaction needs a perceivable invitation. Remove it and you’ve created an affordance gap.