or rha·chis


noun, plural ra·chis·es, rach·i·des [rak-i-deez, rey-ki-] /ˈræk ɪˌdiz, ˈreɪ kɪ-/.

  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.
Ornithology. the part of the shaft of a feather bearing the web.
Anatomy. spinal column.

Nearby words

  1. rachilysis,
  2. rachio-,
  3. rachiocentesis,
  4. rachiometer,
  5. rachiotomy,
  6. rachischisis,
  7. rachitic,
  8. rachitic pelvis,
  9. rachitic rosary,
  10. rachitis

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. 2019

British Dictionary definitions for rachidial



noun plural rachises, rhachises, rachides or rhachides (ˈrækɪˌdiːz, ˈreɪ-)

botany the main axis or stem of an inflorescence or compound leaf
ornithol the shaft of a feather, esp the part that carries the barbs
another name for spinal column
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

Medicine definitions for rachidial


[rā-kĭdē-əl, rə-]


Relating to the vertebral column; spinal.



n. pl. ra•chis•es

spinal column

The American Heritage® Stedman's Medical Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Company. Published by Houghton Mifflin Company.

Science definitions for rachidial



Plural rachises rachides (răkĭ-dēz′, rākĭ-)

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.
The American Heritage® Science Dictionary Copyright © 2011. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.