Hardness is 1) resistance of a material to plastic deformation, usually by indentation which is determined by a standard test where the surface resistance to indentation is measured. The Hardness is dependent on ductility, elastic stiffness, plasticity, strain, strength, toughness, viscoelasticity, and viscosity (Refer to the Brinell Hardness); 2) a water-quality indication of the concentration of inorganic polyvalent cations (generally calcium and magnesium) in water. (Refer to the Water Hardness)

Related Definitions in the Project: The Quality Management; Property and Unit