See more synonyms for hardness on Thesaurus.com
  1. the state or quality of being hard: the hardness of ice.
  2. a relative degree or extent of this quality: wood of a desirable hardness.
  3. that quality in water that is imparted by the presence of dissolved salts, especially calcium sulfate or bicarbonate.
  4. unfeelingness or jadedness; callousness.
  5. harshness or austerity, as of a difficult existence.
  6. South Midland U.S. ill will; bad feelings: There's a lot of hardness between those two boys.
  7. Mineralogy. the comparative ability of a substance to scratch or be scratched by another.Compare Mohs scale.
  8. Metallurgy. the measured resistance of a metal to indention, abrasion, deformation, or machining.

Origin of hardness

before 900; Middle English hardnes, Old English heardnes. See hard, -ness
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2018

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British Dictionary definitions for hardness


  1. the quality or condition of being hard
  2. one of several measures of resistance to indentation, deformation, or abrasionSee Mohs scale, Brinell hardness number
  3. the quality of water that causes it to impair the lathering of soap: caused by the presence of certain calcium salts. Temporary hardness can be removed by boiling whereas permanent hardness cannot
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012

Word Origin and History for hardness

Old English heardnysse; see hard + -ness. Meaning "difficulty of action or accomplishment" is late 14c.

Online Etymology Dictionary, © 2010 Douglas Harper

hardness in Science


  1. A measure of how easily a mineral can be scratched. Hardness is measured on the Mohs scale.
The American Heritage® Science Dictionary Copyright © 2011. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.