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a prefix occurring in loanwords from Latin meaning “on the near side of” (cisalpine); on this model, used in the formation of compound words (cisatlantic).
Chemistry. a specialization of this denoting a geometric isomer having a pair of identical atoms or groups attached on the same side of two atoms linked by a double bond.
Compare trans- (def 2).
< Latin; akin to here


Commonwealth of Independent States.

Commonwealth of Independent States

an alliance of former Soviet republics formed in December 1991, including: Armenia, Azerbaijan, Belarus, Kazakhstan, Kyrgyzstan, Moldova, Russian Federation, Tajikistan, Turkmenistan, Ukraine, and Uzbekistan.
Abbreviation: C.I.S. Unabridged
Based on the Random House Dictionary, © Random House, Inc. 2014.
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Examples from the web for cis
  • cis isomers and trans isomers often have different physical properties.
  • The cis isomer is called maleic acid and the trans is named fumaric acid.
  • In this case, the cis isomer is more stable than the trans isomer.
British Dictionary definitions for cis


Commonwealth of Independent States


on this or the near side of: cisalpine
(often in italics) indicating that two groups of atoms in an unsaturated compound lie on the same side of a double bond: cis-butadiene Compare trans- (sense 5)
Word Origin
from Latin

Commonwealth of Independent States

a loose organization of former Soviet republics, excluding the Baltic States, formed in 1991 CIS
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 cis


word-forming element meaning "on the near side of, on this side," from Latin preposition cis "on this side" (in reference to place or time), related to citra (adv.) "on this side," from PIE *ki-s, from root *ko- "this" (cf. Old Church Slavonic si, Lithuanian šis, Hittite ki "this," Old English hider, Gothic hidre "hither;" see he). Opposed to trans- or ultra-. Originally only of place, sometimes 19c. of time; 21c. of life situations (e.g. cis-gender, by 2011).

Online Etymology Dictionary, © 2010 Douglas Harper
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cis in Medicine

cis (sĭs)
Having two mutations on two genes on the same chromosome of a homologous pair. Often italic.

cis- pref.
Often cis- Having a pair of identical atoms or groups on the same side of a plane that passes through two carbon atoms linked by a double bond: cis-butene.

The American Heritage® Stedman's Medical Dictionary
Copyright © 2002, 2001, 1995 by Houghton Mifflin Company. Published by Houghton Mifflin Company.
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cis in Technology
The Free On-line Dictionary of Computing, © Denis Howe 2010
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Related Abbreviations for cis


  1. Cancer Information System
  2. carcinoma in situ
  3. Commonwealth of Independent States
  4. CompuServe Information Service
The American Heritage® Abbreviations Dictionary, Third Edition
Copyright © 2005 by Houghton Mifflin Company.
Published by Houghton Mifflin Company. All rights reserved.
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