Rheology is the study of the deformation and flow of matter. The term rheology was coined by Eugene Bingham, a professor at Lehigh University, in 1920, from a suggestion by [Markus Reiner]?, inspired by the Heraclitus' famous expression "panta rhei": everything flows.

Basic rheological terms are:

Fluids can be categorized in

- [newtonian fluids]? (the fluid viscosity is constant) and
- [non-newtonian fluids]? (the fluid viscosity depends on the stresses acting on the fluid) which can by subclassified into
- generalized non-newtonian fluids (also called purely viscous fluids) and
- [viscoelastic fluids]?.

Rheological properties are determined by means of rheometry?.