Linked from
The 10 pages that link to Kinematic viscosity, each with the reason it gives.
ViscosityBroader topic: It expresses viscous diffusion while accounting for fluid density.
Reynolds numberRelated: It is the fluid property used with speed and length in the common formula.
Lattice Boltzmann methodRelated: In common collision models, it is set by the relaxation time.
Law of the wallRelated: It sets the viscous length used to scale distance from the wall.
Rayleigh problemRelated: It sets the rate at which the plate’s motion spreads into the fluid.