Noun
The quality or state of being hard, literally or figuratively.
The cohesion of the particles on the surface of a body, determined by its capacity to scratch another, or be itself scratched;-measured among minerals on a scale of which diamond and talc form the extremes.
The peculiar quality exhibited by water which has mineral salts dissolved in it. Such water forms an insoluble compound with soap, and is hence unfit for washing purposes.
Source: Webster's dictionaryThere is only one quality worse than hardness of heart and that is softness of head. Theodore Roosevelt
The hardness of God is kinder than the softness of men, and His compulsion is our liberation. C. S. Lewis
A hardness such as this is taught by rough experience and despair alone. Anne Brontë
...that very loyalty to the past with its dream of beauty and with its real hardness and hardships. These things save us from what is the greatest peril of our age, the peril of materialism.... The struggle against materialism in the hearts of our people is one of the greatest struggles of this age. Stanley Baldwin
Hardness shatters; strength endures. Robert Jordan
An egg shouldn't be deceived by the hardness of its shell; it cannot challenge a stone in a fight. African Proverb