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