• synonyms


  1. Also isosmotic. Physical Chemistry. noting or pertaining to solutions characterized by equal osmotic pressure.Compare hypertonic(def 2), hypotonic(def 2).
  2. Physiology.
    1. noting or pertaining to a solution containing the same salt concentration as mammalian blood.
    2. noting or pertaining to a muscular contraction in which constant tension continues while the length of the muscle decreases, as during mechanical work.
  3. Music. of or characterized by equal tones.
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Origin of isotonic

1820–30; < Greek isóton(os) having equal accent or tone (see iso-, tone) + -ic
Related formsi·so·to·nic·i·ty [ahy-suh-tuh-nis-i-tee] /ˌaɪ sə təˈnɪs ɪ ti/, noun
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2018

Examples from the Web for isotonic

Historical Examples

  • All nose lotions should be alkaline, and isotonic with the blood plasma.

    A System of Operative Surgery, Volume IV (of 4)


  • Normal saline solution is isotonic with the body cells and hence is employed as the vehicle.

    The Fundamentals of Bacteriology

    Charles Bradfield Morrey

  • Take, for instance, two isotonic solutions, one of salt and another of sugar.

  • It may be objected that segmentation is also produced by a solution which is isotonic with sea water.

British Dictionary definitions for isotonic


  1. physiol (of two or more muscles) having equal tension
  2. (of a drink) designed to replace the fluid and salts lost from the body during strenuous exercise
  3. Also: isosmotic (of two solutions) having the same osmotic pressure, commonly having physiological osmotic pressureCompare hypertonic, hypotonic
  4. music of, relating to, or characterized by the equal intervals of the well-tempered scaleisotonic tuning
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Derived Formsisotonicity (ˌaɪsəʊtəʊˈnɪsɪtɪ), noun
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 isotonic


1828, from Greek isotonos "of level pitch; equally stretched," from iso- (see iso-) + tonos (see tenet).

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Online Etymology Dictionary, © 2010 Douglas Harper

isotonic in Medicine


  1. Of equal tension.
  2. Isosmotic.
  3. Having the same concentration of solutes as the blood.
  4. Of or involving muscular contraction in which the muscle remains under relatively constant tension while its length changes.
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Related formsi′so•to•nici•ty (-tə-nĭsĭ-tē) n.
The American Heritage® Stedman's Medical Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Company. Published by Houghton Mifflin Company.