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rachis

or rha·chis

[rey-kis]
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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

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British Dictionary definitions for rachis

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

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

rachis in Medicine

rachis

(rākĭs)
n. pl. ra•chis•es
  1. spinal column

rachis in Science

rachis

[rākĭs]