rheology

Rheology (; ) is the study of the flow of matter, primarily in a fluid (liquid or gas) state, as well as "soft solids", which experience conditions under which they respond with plastic flow rather than elastic deformation to forces applied to them. Rheology is the branch of physics that deals with the deformation and flow of materials, both solids and liquids.

The term rheology was coined by Eugene C. Bingham, a professor at Lafayette College, in 1920 from a suggestion by a colleague, Markus Reiner. The term was inspired by the aphorism of Heraclitus (often mistakenly attributed to Simplicius), (, 'everything flows') and was first used to describe the flow of liquids and the deformation of solids. It applies to substances that have a complex microstructure, such as muds, sludges, suspensions, and polymers and other glass formers (e.g., silicates), as well as many foods and additives, bodily fluids (e.g., blood) and other biological materials, and other materials that belong to the class of soft matter such as food.