hard·​ness | \ˈhärd-nəs \

Definition of hardness 

1 : the quality or state of being hard

2a : 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

Keep scrolling for more

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

Adjust the calcium hardness by using calcium chloride. Danielle Beurteaux, Popular Mechanics, "How to Get Your Swimming Pool Ready for Summer," 18 May 2018 This is directly dependent on the hardness of the water. Danielle Beurteaux, Popular Mechanics, "How to Get Your Swimming Pool Ready for Summer," 18 May 2018 More intimate than a typical period drama, the movie becomes an unexpectedly intense, racking examination of Mary’s psychology: her impulsiveness, her defiance, the almost frightening hardness at her core. Jamie Hawkesworth, Vogue, "Saoirse Ronan on Growing Up on Camera, the Changing Politics of Ireland, and Becoming a Queen," 11 July 2018 And while the cast (which also includes Melissa Miller in dual roles) is uniformly strong, the blend of hardness and heartbreak that Meaney displays is especially affecting. James Hebert, sandiegouniontribune.com, "A struggle to cling to identity is at heart of La Jolla Playhouse's quietly moving 'Queens'," 10 July 2018 Those included low pressure (12 percent); bad taste (11 percent); water hardness (8 percent); discoloration (8 percent); bad smell (6 percent); and high lead/mineral content (4 percent). Robert Higgs, cleveland.com, "Cleveland water system trails the Midwest in J.D. Power customer satisfaction study," 15 May 2018 If used as directed, my nails definitely improve in strength and hardness (compared with my usual soft and vulnerable condition). Ellen Warren, chicagotribune.com, "Help for weak nails: Readers share what works," 16 Apr. 2018 Beers, meanwhile, is out here testing rubber hardness—and more. Cam Wolf, GQ, "An Ex-Nike Designer Is Here to Revolutionize Sneaker YouTube," 19 Apr. 2018 That extraordinary hardness arises from a strong and inflexible structure: Five atoms form a tetrahedron and share electron pairs with each other. 3. Gemma Tarlach, Discover Magazine, "20 Things You Didn't Know About ... Diamonds," 23 Mar. 2018

These example sentences are selected automatically from various online news sources to reflect current usage of the word 'hardness.' Views expressed in the examples do not represent the opinion of Merriam-Webster or its editors. Send us feedback.

See More

First Known Use of hardness

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

Keep scrolling for more

Learn More about hardness

Statistics for hardness

Last Updated

26 Sep 2018

Look-up Popularity

Time Traveler for hardness

The first known use of hardness was before the 12th century

See more words from the same century

Keep scrolling for more

More Definitions for hardness



English Language Learners Definition of hardness

: the quality or state of being hard

Keep scrolling for more

Comments on hardness

What made you want to look up hardness? Please tell us where you read or heard it (including the quote, if possible).


playful or foolish behavior

Get Word of the Day daily email!

Test Your Vocabulary

Autumn Words of the Day 2018

  • a-top-down-image-of-road-through-an-autumn-forest
  • Which is a synonym of fugacious?
Name That Thing

Test your visual vocabulary with our 10-question challenge!

Word Winder's CrossWinder

Test Your Knowledge - and learn some interesting things along the way.


Love words? Need even more definitions?

Subscribe to America's largest dictionary and get thousands more definitions and advanced search—ad free!