z The spreading of an innovation or idea through a fixed population in such a way that the number of those adopting grows continuously larger, resulting in an expanded area of dissemination
z The distance-controlled spreading of an idea, innovation, or some other item through a local population by contact from person to person
z Two types
z Analogous to the communication of a contagious disease
z A form of diffusion in which an idea or innovation spreads by “trickling down” from larger to smaller adopting units
z An urban hierarchy is usually involved, encouraging the leapfrogging of innovations over wider areas, with geographic distance a less important factor.