Diffusivity

Diffusivity is a rate of diffusion, a measure of the rate at which particles or heat or fluids can spread.

It is measured differently for different mediums.

Diffusivity may refer to:
 * Thermal diffusivity, diffusivity of heat
 * Diffusivity of mass:
 * Mass diffusivity, molecular diffusivity (often called "diffusion coefficient")
 * Eddy diffusion, eddy diffusivity
 * Kinematic viscosity, characterising momentum diffusivity
 * Magnetic diffusivity

Dimensions and units
Diffusivity has dimensions of length2 / time, or m2/s in SI units and cm2/s in CGS units.