Permeability (often symbolized by κ or k) is the ability of materials to allow fluids to pass through them. The term is used in fluid dynamics and geology. The common measure of permeability is defined by Darcy Velocity Field, i.e., it can be stated by testing a material and plugging values into the equation and represents the contribution of the type of porous material to the rate at which fluid passes through.
The term Permeability is also used in Electromagnetism (Magnetic Permeability, μ), in effect, treating a Magnetic Field as a fluid and quantifying a material's ability to allow the magnetic field lines to pass through (occur in) the material.
Darcy Velocity Field