Permeability is a measure of how easily fluids can penetrate and flow through a solid. Solids are permeable because they have networks of pore spaces through which fluids can flow.
Permeability is an important property of building materials and textiles. The permeability of sedimentary rocks like sandstone and limestone, through which flow water and oil into wells, has been the most carefully studied.
Magnetic permeability is a property of a substance which tells how much it becomes magnetized when placed in a magnetic field. The higher the magnetic permeability of a substance, the more highly magnetized it becomes when placed in a magnetic field.
Permeability is also a property of semipermeable membranes. In this case, permeability is a measure of how rapidly a substance on one side of the membrane can diffuse through the membrane to the other side. The membranes around plant and animal cells are selectively permeable. These membranes will allow certain ions to pass through but will not permit other ions to pass.
