For a @N04138@, the shear @V06627@ is often termed simply @V06627@ since in most situations it is the only one considered. It relates the shear components of stress and those of rate of @S06037@ at a point in the fluid by: \[\sigma _{xy}=\sigma _{yx}=\eta \ (\frac{\partial \nu_{x}}{\partial y}+\frac{\partial \nu_{y}}{\partial x})=2\ \eta \ \overset{\text{.}}{\gamma }_{yx}\] where \(\overset{\text{.}}{\gamma }_{yx}\), the shear component of rate of @S06037@ is defined as follows: \[\overset{\text{.}}{\gamma }_{yx}=\frac{1}{2}\ (\frac{\partial \nu_{x}}{\partial y}+\frac{\partial \nu_{y}}{\partial x})\] Corresponding relations hold for \(\sigma _{xz}\) and \(\sigma _{yz}\); \(\sigma _{xy}\) is the component of stress acting in the \(y\)-direction on a plate normal to the \(x\)-axis; \(\nu_{x}\), \(\nu_{y}\), \(\nu_{z}\) are the components of velocity.