• noun the ability of a rock to allow water to pass through it
  • noun the ability of a membrane to allow fluid or chemical substances to pass through it


  • The property of a material that permits passage of water vapor.
  • The property of soil which permits the flow of water.


  • Its symbol is μ. A quantitative indicator of the response of a material or medium to a magnetic field. It is expressed by the following formula: μ = B/H, where B is the magnetic flux density of the material or medium, and H is the strength of the surrounding magnetic field. Relative permeability is obtained using the following formula: μr = μ/μ0, where μr is relative permeability, and μ0 is the permeability of free space. The absolute permeability of free space is a physical constant equal to approximately 1.256637 × 10-6 henry per meter, and its relative permeability is equal to 1, as seen by the this formula. Materials whose relative permeability is less than 1 are diamagnetic, those slightly above 1 are paramagnetic, and those substantially above 1 are ferromagnetic. Also known as magnetic permeability.
  • The quality or state of being permeable.