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[trahy-soh-mee] /ˈtraɪ soʊ mi/
noun, Pathology.
an abnormality characterized by the presence of an additional chromosome to the normal diploid number.
Origin of trisomy
First recorded in 1925-30; tri- + -some3 + -y3 Unabridged
Based on the Random House Dictionary, © Random House, Inc. 2018.
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British Dictionary definitions for trisomy


the condition of having one chromosome of the set represented three times in an otherwise diploid organism, cell, etc. Trisomy of chromosome 21 results in Down's syndrome
Derived Forms
trisomic (traɪˈsəʊmɪk) adjective
Word Origin
C20: from tri- + (chromo)som(e) + -y³
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 trisomy

1930, from trisomic (1921), from tri- + ending from chromosome.

Online Etymology Dictionary, © 2010 Douglas Harper
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trisomy in Medicine

trisomy tri·so·my (trī-sō'mē, trī'sō'-)
The condition of having three copies of a given chromosome or chromosome segment in each somatic cell rather than the normal number of two.

tri·so'mic adj.
The American Heritage® Stedman's Medical Dictionary
Copyright © 2002, 2001, 1995 by Houghton Mifflin Company. Published by Houghton Mifflin Company.
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trisomy in Science
  (trī-sō'mē, trī'sō'-)   
The condition of having three copies of a given chromosome in each body cell rather than the normal number of two.
The American Heritage® Science Dictionary
Copyright © 2002. Published by Houghton Mifflin. All rights reserved.
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