the axis of an inflorescence when somewhat elongated, as in a raceme.
(in a pinnately compound leaf or frond) the prolongation of the petiole along which the leaflets are disposed.
any of various axial structures.
Ornithology. the part of the shaft of a feather bearing the web.
- ra·chid·i·an [ruh-kid-ee-uhn], /rəˈkɪd i ən/, ra·chi·al [rey-kee-uhl], /ˈreɪ ki əl/, ra·chid·i·al, adjective
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2023
How to use rachis in a sentence
The pinnules are from a line to two lines long, and are adnate to the secondary rachis by a more or less decurrent base.Beautiful Ferns | Daniel Cady Eaton
The stipes is somewhat longer than the rachis, and it is of a whity-green colour.How to Know the Ferns | S. Leonard Bastin
A simple inflorescence of flowers on pedicels of equal length arranged on a common, elongated axis (rachis).Michigan Trees | Charles Herbert Otis
A simple inflorescence of sessile flowers arranged on a common, elongated axis (rachis).Michigan Trees | Charles Herbert Otis
Under these conditions the midvein is called the rachis (a), and the divisions are called the pinn (b).How to Know the Ferns | Frances Theodora Parsons
British Dictionary definitions for rachis
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
- rachial or rhachial (ˈreɪkɪəl) or rachidial or rhachidial (rəˈkɪdɪəl), adjective
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
Scientific definitions for rachis
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.