As a concept, affordance is integral to scholarly analysis across multiple fields—including media studies, science and technology studies, communication studies, ecological psychology, and design studies among others. Critics, however, rightly point to the following shortcomings: definitional confusion, a false binary in which artifacts either afford or do not, and failure to account for diverse subject-artifact relations. Addressing these critiques, this article demarcates the mechanisms of affordance—as artifacts request, demand, allow, encourage, discourage, and refuse—which take shape through interrelated conditions: perception, dexterity, and cultural and institutional legitimacy. Together, the mechanisms and conditions constitute a dynamic and structurally situated model that addresses how artifacts afford, for whom and under what circumstances.