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[huh-mol-uh-guh s, hoh-] /həˈmɒl ə gəs, hoʊ-/
having the same or a similar relation; corresponding, as in relative position or structure.
corresponding in structure and in origin, but not necessarily in function:
The wing of a bird and the foreleg of a horse are homologous.
having the same alleles or genes in the same order of arrangement:
homologous chromosomes.
Chemistry. of the same chemical type, but differing by a fixed increment of an atom or a constant group of atoms:
Methyl and ethyl alcohols are homologous.
Immunology. pertaining to an antigen and its specific antibody.
Origin of homologous
1650-60; < Medieval Latin homologus < Greek homólogos agreeing, equivalent to homo- homo- + -logos proportional, equivalent to log- (stem of lógos proportion; see logos) + -os -ous
Related forms
nonhomologous, adjective
unhomologous, adjective Unabridged
Based on the Random House Dictionary, © Random House, Inc. 2018.
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British Dictionary definitions for homologous


/həʊˈmɒləɡəs; hɒ-/
having a related or similar position, structure, etc
(chem) (of a series of organic compounds) having similar characteristics and structure but differing by a number of CH2 groups
  1. (of two or more tissues) identical in structure
  2. (of a vaccine) prepared from the infecting microorganism
(biology) (of organs and parts) having the same evolutionary origin but different functions: the wing of a bat and the paddle of a whale are homologous Compare analogous (sense 2)
(maths) (of elements) playing a similar role in distinct figures or functions
Derived Forms
homologically, adverb
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
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Word Origin and History for homologous

1650s, from Greek homologos "agreeing, of one mind," from homos "same" (see homo- (1)) + logos "relation, reasoning, computation," related to legein "reckon, select, speak" (see lecture (n.)).

Online Etymology Dictionary, © 2010 Douglas Harper
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homologous in Medicine

homologous ho·mol·o·gous (hə-mŏl'ə-gəs, hō-)

  1. Corresponding or similar in position, value, structure, or function.

  2. Similar in structure and evolutionary origin, though not necessarily in function.

  3. Relating to the correspondence between an antigen and the antibody produced in response to it.

  4. Having the same morphology and linear sequence of gene loci as another chromosome.

  5. Belonging to or being a series of organic compounds each successive member of which differs from the preceding member by a constant increment, especially by an added CH2 group.

The American Heritage® Stedman's Medical Dictionary
Copyright © 2002, 2001, 1995 by Houghton Mifflin Company. Published by Houghton Mifflin Company.
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homologous in Science
  1. Similar in structure and evolutionary origin but having different functions, as a human's arm and a seal's flipper.

  2. Being one of a pair of chromosomes, one from the female parent and one from the male parent, that have genes for the same traits in the same positions. Genes on homologous chromosomes may not have the same form, however. For example, one chromosome in a pair of homologous chromosomes may contain a gene for brown eyes, and the other a gene for blue eyes. Human females have 23 pairs of homologous chromosomes (including the two X chromosomes), while human males have 22 because the Y chromosome is not paired.

  3. Belonging to or being a series of organic compounds, each successive member of which differs from the preceding member by a constant increment, especially by an added CH2 group. The alkanes (methane, ethane, propane, and others) are a homologous series of compounds.

  4. Involving organisms of the same species, as in grafted body tissues.

The American Heritage® Science Dictionary
Copyright © 2002. Published by Houghton Mifflin. All rights reserved.
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