hardness
hard-ness
noun
The measure of dissolved mineral salts, especially calcium and magnesium, in water.
"Water hardness can cause limescale in kettles."
noun
A lack of sympathy or kindness; a severe or unfeeling nature.
"There was a hardness in his eyes."
noun
The quality of being firm, rigid, or resistant to pressure and breaking.
"The diamond's hardness makes it useful for cutting."
Thesaurus
Synonyms: stiffness, rigourousness, rigour, harshness, severity, rigor, severeness, inclemency, rigorousness, callousness, callosity, insensibility
Antonyms: softness