Rheology has been defined as “the science of the deformation and flow of matter”. In theory it could include the study of all materials that deform or flow but, by convention, classical (Hookean) elastic solids and viscous (Newtonian) liquids are excluded. Both non-Newtonian and elastic liquids and viscoelastic solids are included in the science.
The Rheometer is an instrument that measures the viscoelastic properties of materials. The Rheometer is capable of measure not only the shear viscosity of fluids, but also other viscoelastic properties, such as: Storage Modulus (G’), Loss Modulus (G’’), tan delta and time-dependent properties such as Stress Relaxation Modulus and Creep & Recoverable Compliance.