Network diffusion describes how something spreads out or diffuses along the connections of a network as a function of the properties of its nodes and the structure of connectivity within the system. The classic example of this being the diffusion of a disease through some population, but we might be dealing with how the loss of one species in an ecosystem has an effect on others, the spread of financial contagion from one institution to another, or the spread of some information within a group of people. This spreading on a network is called network propagation or diffusion.