What is Apparent viscosity?

In fluid mechanics, apparent viscosity is the shear stress applied to a fluid divided by the shear rate:

For a Newtonian fluid, the apparent viscosity is constant, and equal to the Newtonian viscosity of the fluid, but for non-Newtonian fluids, the apparent viscosity depends on the shear rate. Apparent viscosity has the SI derived unit Pa·s , but the centipoise is frequently used in practice:.