There are two dimensionless groups named Taylor number. The first is used as a criterion for the stability of flow in an annulus surrounding a rotating cylinder.

where ω is angular velocity (s^{−1}), R_{a} is the mean radius of the annulus, a is the width of the annulus, and ν is fluid kinematic viscosity. (Sometimes the square of this quantity is used to define Taylor number, see Taylor Instability.)

The second Taylor number represents the square of the ratio of **Coriolis Force** to viscous force, i.e.,