rachis

American  

[rey-kis] / ˈreɪ kɪs /

Or rhachis

noun

plural

rachises, rachides

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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rachis British  

/ ˈreɪkɪs, ˈreɪkɪəl, rəˈkɪdɪəl /

noun

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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rachis Scientific  

/ rā′kĭs /

plural

rachises

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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Other Word Forms

• rachial
  adjective
• rachidial
  adjective
• rachidian
  adjective

Etymology

Origin of rachis

1775–85; < New Latin < Greek rháchis spine, ridge, backbone

Example Sentences

Each leaflet may have its own stalk, but is attached to the rachis.

From Textbooks • Jun. 9, 2022

“The thickness of the rachis in some specimens is 3 microns thick. That’s less than the size of the average cell,” O’Connor says.

From Science Magazine • Dec. 14, 2018

That combination of features—weak rachis and evenly-spaced barbules—has not previously been directly observable in the flattened 2-dimensional fossils, Holtz says.

From Science Magazine • Dec. 8, 2016

That is interesting because the rachis seems to aid in flight.

From New York Times • Dec. 8, 2016

Using my HB pencil, I work to sketch out the barbs of the feather, drawing lines from the rachis outward.

From "Red Flags and Butterflies" by Sheryl Azzam

Related Words

• bone
• vertebrae