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
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 grounds crew tests soil moisture content, court hardness wear and plant chlorophyll levels to dictate evening watering amounts.
—
Tim Newcomb, Forbes.com, 7 July 2025
As such, prolonged use may reduce the surface hardness of tooth enamel.2
Studies in which hydrogen peroxide was used daily for up to six years in concentrations of 3% or less have reported only occasional and temporary irritation in the mouth.
—Anna Giorgi, Verywell Health, 12 May 2025
Minerals like calcium and magnesium can cling to the surface over time, especially in areas with high water hardness.
—Daley Quinn, Southern Living, 1 July 2025
Generally speaking, high-quality Western knives have 59-62 HRC, a measurement of the hardness of materials, whereas Japanese knives’ HRC ranges from 60 to 65.
—Akiko Katayama, Forbes.com, 13 June 2025
See All Example Sentences for hardness
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Tim Newcomb, Forbes.com, 7 July 2025
As such, prolonged use may reduce the surface hardness of tooth enamel.2
Studies in which hydrogen peroxide was used daily for up to six years in concentrations of 3% or less have reported only occasional and temporary irritation in the mouth.
—Anna Giorgi, Verywell Health, 12 May 2025
Minerals like calcium and magnesium can cling to the surface over time, especially in areas with high water hardness.
—Daley Quinn, Southern Living, 1 July 2025
Generally speaking, high-quality Western knives have 59-62 HRC, a measurement of the hardness of materials, whereas Japanese knives’ HRC ranges from 60 to 65.
—Akiko Katayama, Forbes.com, 13 June 2025
See All Example Sentences for hardness
Cite this Entry
“Hardness.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/hardness. Accessed 8 Aug. 2025.
Copy CitationKids 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
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