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iso-

  1. a combining form meaning “equal,” used in the formation of compound words: isochromatic; in chemistry, used in the names of substances which are isomeric with the substance denoted by the base word: isocyanic acid.
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Also especially before a vowel, is-.

Origin of iso-

< Greek, combining form of ísos equal
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2018

British Dictionary definitions for iso-

iso-

before a vowel is-

combining form
  1. equal or identicalisomagnetic
  2. indicating that a chemical compound is an isomer of a specified compoundisobutane; isocyanic acid
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Word Origin for iso-

from Greek isos equal
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 iso-

word-forming element meaning "equal, similar, identical; isometric," from comb. form of Greek isos "equal to, the same as" (e.g. isometor "like one's mother"). Used properly only with words of Greek origin; the Latin equivalent is equi- (see equi-).

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Online Etymology Dictionary, © 2010 Douglas Harper

iso- in Medicine

iso-

pref.
  1. Equal; uniform:isobar.
  2. Isomeric:isopropyl.
  3. Characterized by sameness with respect to species:isoantigen.
  4. Characterized by sameness with respect to genotype:isograft.
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The American Heritage® Stedman's Medical Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Company. Published by Houghton Mifflin Company.

iso- in Science

iso-

  1. A prefix that means “equal,” as in isometric, “having equal measurements.”
  2. A prefix used to indicate an isomer of an organic compound, especially a branched isomer of a compound that normally consists of a straight chain. The isomer is characterized by a Y-shaped branch at the end of the chain that consists of two “prongs”. Each prong consists of one carbon atom. Thus isopentane contains five carbon atoms like normal pentane, but arranged as a chain of three carbons plus a Y-shaped branch of two carbons at the end.
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The American Heritage® Science Dictionary Copyright © 2011. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.