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rachis

or rha·chis

[rey-kis]
noun, plural ra·chis·es, rach·i·des [rak-i-deez, rey-ki-] /ˈræk ɪˌdiz, ˈreɪ kɪ-/.
  1. Botany.
    1. the axis of an inflorescence when somewhat elongated, as in a raceme.
    2. (in a pinnately compound leaf or frond) the prolongation of the petiole along which the leaflets are disposed.
    3. any of various axial structures.
  2. Ornithology. the part of the shaft of a feather bearing the web.
  3. Anatomy. spinal column.
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Origin of rachis

1775–85; < New Latin < Greek rháchis spine, ridge, backbone
Related formsra·chid·i·an [ruh-kid-ee-uh n] /rəˈkɪd i ən/, ra·chi·al [rey-kee-uh l] /ˈreɪ ki əl/, ra·chid·i·al, adjective
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2018

British Dictionary definitions for rachidial

rachis

rhachis

noun plural rachises, rhachises, rachides or rhachides (ˈrækɪˌdiːz, ˈreɪ-)
  1. botany the main axis or stem of an inflorescence or compound leaf
  2. ornithol the shaft of a feather, esp the part that carries the barbs
  3. another name for spinal column
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Derived Formsrachial or rhachial (ˈreɪkɪəl) or rachidial or rhachidial (rəˈkɪdɪəl), adjective

Word Origin for rachis

C17: via New Latin from Greek rhakhis ridge
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

rachidial in Medicine

rachidial

(rā-kĭdē-əl, rə-)
adj.
  1. Relating to the vertebral column; spinal.
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rachis

(rākĭs)
n. pl. ra•chis•es
  1. spinal column
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The American Heritage® Stedman's Medical Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Company. Published by Houghton Mifflin Company.

rachidial in Science

rachis

[rākĭs]
Plural rachises rachides (răkĭ-dēz′, rākĭ-)
  1. A main axis or shaft, such as the main stem of an inflorescence, the stalk of a pinnately compound leaf, the shaft of a feather, or the spinal column.
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The American Heritage® Science Dictionary Copyright © 2011. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.