hardness

From hard +‎ -ness.

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hardness (countable and uncountable, plural hardnesses)

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

• hardiness

• hardness in Webster’s Revised Unabridged Dictionary, G. & C. Merriam, 1913.

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