hardness

noun

1. (countable, uncountable)The quality of being hard.

   “Who can number the cloudes in wiſedom? or who can ſtay the bottles of heauen, / When the duſt groweeh^([sic – meaning groweth]) into hardneſſe and the clods cleaue faſt together?”

2. (countable, uncountable)An instance of this quality; hardship.
3. (countable, uncountable)The quantity of calcium carbonate dissolved in water, usually expressed in parts per million (ppm).
4. (countable, uncountable)The resistance to scratching, cutting, indentation or abrasion of a metal or other solid material.
5. (countable, uncountable)The penetrating ability of electromagnetic radiation, such as x-rays; generally, the shorter the wavelength, the harder and more penetrating the radiation.
6. (countable, uncountable)The measure of resistance to damage of a facility, equipment, installation, or telecommunications infrastructure when subjected to attack.
7. (countable)A measure of how hard a material is.

   “The hardness of the material was high.”

   ““This material has a specific hardness and is chemically very stable. It forms naturally from calcium alone, but bacteria accelerate the transformation into calcium carbonate,” explains Alejandro Montesinos, head of the Decarbonization, Climate Change, and Circular Economy Research Group at Tec de Monterrey and a member of the Institute of Advanced Materials and Sustainable Manufacturing.”