Rheology 's the study of the flow of matter: mainly liquids but also soft solids or solids under conditions in which they flow rather than deform elastically. It applies to substances which have a complex structure, including muds, sludges, suspensions, polymers, many foods, bodily fluids, and other biological materials. The flow of these substances can't be characterized by a single value of viscosity (at a fixed temperature) - instead the viscosity changes due to other factors. For example ket… (More on Rheology)