Definition of hardnesses:
(n) :
The quality of being hard.
(n) :
The resistance to scratching, cutting, indentation or abrasion of a metal or other solid material.
(n) :
An instance of this quality; hardship.
(n) :
(countable, engineering) A measure of how hard a material is
(n) :
(inorganic chemistry) The quantity of calcium carbonate dissolved in water, usually expressed in parts per million (ppm).
(n) :
(physics) The penetrating ability of electromagnetic radiation, such as x-rays; generally, the shorter the wavelength, the harder and more penetrating the radiation.