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

• adversity
• asperity
• difficulty
• hardship
• rigor

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

The severity of water spots varies depending on your local water hardness. —Nafeesah Allen, Better Homes & Gardens, 2 June 2025

The hardness of seats, even those that recline flat into a bed, is a common pain point for many customers on long-haul flights. —Eileen Falkenberg-Hull, MSNBC Newsweek, 20 May 2025

Routine tests are ran every few hours to check water quality through pH, chlorine, phosphate, fluoride, alkalinity, total hardness, calcium hardness, turbidity and the Langelier Saturation Index, which determines water balance. —Olivia Stevens, Chicago Tribune, 30 Apr. 2025

Also add calcium chloride if the water's calcium level (hardness) is too low. —Brandee Gruener, Southern Living, 21 Apr. 2025

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