For systems showing non-Newtonian behaviour when measured in steady @[email protected], a @[email protected] \(\eta \) equal to \(\frac{\sigma}{D}\) at a given value of the @[email protected] \(D\), where \(\sigma \) is the stress; \(\eta _{0}\) is the limiting @[email protected] at zero @[email protected], and \(\eta _{\infty }\) the limiting @[email protected] at infinite @[email protected]; \(\text{[}\eta _{0}\text{]}\) is the limit of @[email protected] at zero shear.