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From Middle English hardness, from Old English heardness, from heard + -ness. Equivalent to hard +‎ -ness.



hardness (countable and uncountable, plural hardnesses)

  1. The quality of being hard.
    • c. 1380s, [Geoffrey Chaucer; William Caxton, editor], The Double Sorow of Troylus to Telle Kyng Pryamus Sone of Troye [...] [Troilus and Criseyde], [Westminster]: Explicit per Caxton, published 1482, OCLC 863541017; republished in [William Thynne], editor, The Workes of Geffray Chaucer Newlye Printed, [], book II, [London]: [] [Richard Grafton for] Iohn Reynes [], 1542, OCLC 932884868, folio clxxx, recto:
      For truſteth wel, to longe ydone hardneſſe / Cauſeth diſpyte ful often for diſtreſſe
      For trust this well: Too long maintained hardness / Creates contempt from distress.
    • a. 1460, Reginald Pecock, Elsie Vaughan Hitchcock, editor, The Donet, Early English Text Society, published 1921:
      As it is forto se þingis present to þe siȝt, heere þe sown present to þe eeris, touche hardnesse, neischnes, heet, or coold present to þe touche, & so forþe of oþire.
      As it is to see things present to the sight, here the sound present to the ears, touch hardness, softness, heat, or cold present to the touch, and so forth of others.
    • 1611, The Holy Bible, [] (King James Version), London: [] Robert Barker, [], OCLC 964384981, Job 38:37–38:
      Who can number the cloudes in wiſedom? or who can ſtay the bottles of heauen, / When the duſt groweeh[sic, meaning groweth] into hardneſſe and the clods cleaue faſt together?
  2. An instance of this quality; hardship.
  3. (inorganic chemistry) The quantity of calcium carbonate dissolved in water, usually expressed in parts per million (ppm).
  4. The resistance to scratching, cutting, indentation or abrasion of a metal or other solid material.
  5. (physics) The penetrating ability of electromagnetic radiation, such as x-rays; generally, the shorter the wavelength, the harder and more penetrating the radiation.
  6. The measure of resistance to damage of a facility, equipment, installation, or telecommunications infrastructure when subjected to attack.


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