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. Rheology has important applications in the engineering sciences and in physiology. Hemorheology is the study of the flow properties of blood.

Basic rheological terms are:

  • Viscosity
  • Shear rate and elongation rate
  • Shear stress
  • Newtonian law

Fluids can be categorized as:
  • 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.

Journals covering rheology include: