hardness

noun

hard·​ness ˈhärd-nəs 

1

: the quality or state of being hard

2

a

: the cohesion of the particles on the surface of a mineral as determined by its capacity to scratch another or be itself scratched compare mohs' scale

b

: resistance of metal to indentation under a static load or to scratching

Synonyms of hardness

• hardship
• difficulty

Examples of hardness in a Sentence

the hardness of a diamond

The wood's hardness makes it suitable for carving.

Recent Examples on the Web

To lead a child to a gas chamber demands a hardness of heart that must be cultivated. — Literary Hub, 18 Sep. 2026

Applications Across High-Temperature Industries The combination of optical performance, hardness and temperature resistance makes sapphire useful across several technology sectors. — Prabhat Ranjan Mishra, Interesting Engineering, 17 Sep. 2026

The one currently taking shape in his workshop is among the difficult ones, Goh said, because of the hardness of the wood. — ABC News, 17 Sep. 2026

In a Water Filter Guru review of the FilterBaby Pro, hardness measured 250 ppm before filtration and 251 ppm after. — Ryan Brennan, Miami Herald, 16 Sep. 2026

Word History

First Known Use

before the 12th century, in the meaning defined at sense 1

Phrases Containing hardness

• Brinell hardness
• Brinell hardness number

Rhymes for hardness

• microhardness

Kids Definition

hardness

noun

hard·​ness ˈhärd-nəs 

1

: the quality or state of being hard

2

: the ability of a substance (as a mineral) to scratch another substance or be itself scratched