follow Dictionary.com

Stories We Like: Novels For Language Lovers

chiasma

[kahy-az-muh] /kaɪˈæz mə/
noun, plural chiasmas, chiasmata
[kahy-az-muh-tuh] /kaɪˈæz mə tə/ (Show IPA)
1.
Anatomy. a crossing or decussation, as that of the optic nerves at the base of the brain.
2.
Cell Biology. a point of overlap of paired chromatids at which fusion and exchange of genetic material take place during prophase of meiosis.
Also, chiasm
[kahy-az-uh m] /ˈkaɪ æz əm/ (Show IPA)
.
Origin
1830-1840
1830-40; < Greek: crosspiece of wood, cross-bandage, equivalent to chi chi1 + -asma noun suffix
Related forms
chiasmal, chiasmic, chiasmatic
[kahy-az-mat-ik] /ˌkaɪ æzˈmæt ɪk/ (Show IPA),
adjective
Dictionary.com Unabridged
Based on the Random House Dictionary, © Random House, Inc. 2014.
Cite This Source
Examples from the web for chiasma
  • Within the chiasma, the optic nerves undergo a partial decussation.
  • The fibers forming the medial part of each tract and posterior part of the chiasma have no connection with the optic nerves.
  • The optic chiasma is formed by the meeting and partial decussation of the fibers of the two optic nerves.
  • Behind the chiasma the fibers grow backward as the optic tracts to the thalami and mid-brain.
British Dictionary definitions for chiasma

chiasma

/kaɪˈæzmə/
noun (pl) -mas, -mata (-mətə), -asms
1.
(cytology) the cross-shaped connection produced by the crossing over of pairing chromosomes during meiosis
2.
(anatomy) the crossing over of two parts or structures, such as the fibres of the optic nerves in the brain
Derived Forms
chiasmal, chiasmic, adjective
Word Origin
C19: from Greek khiasma wooden crosspiece, from khiazein to mark with an X, from khichi1
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
Cite This Source
Word Origin and History for chiasma
n.

"a crossing," 1832, medical Latin, from Greek khiasma "two things placed crosswise," which is related to khiasmos (see chiasmus). In cytology from 1911.

Online Etymology Dictionary, © 2010 Douglas Harper
Cite This Source
chiasma in Medicine

chiasma chi·as·ma (kī-āz'mə) or chi·asm (kī'āz'əm)
n. pl. or chi·as·mas, chi·as·ma·ta (-mə-tə), chi·as·ms

  1. A crossing or intersection of two tracts, as of nerves or ligaments.

  2. The point of contact between paired chromatids during meiosis, resulting in a cross-shaped configuration and representing the cytological manifestation of crossing over.


chi·as'mal or chi·as'mic or chi'as·mat'ic (-māt'ĭk) adj.
The American Heritage® Stedman's Medical Dictionary
Copyright © 2002, 2001, 1995 by Houghton Mifflin Company. Published by Houghton Mifflin Company.
Cite This Source

Word of the Day

Difficulty index for chiasma

Some English speakers likely know this word

Word Value for chiasma

14
15
Scrabble Words With Friends

Nearby words for chiasma