rachis

or rha·chis

[ rey-kis ]

noun

, plural ra·chis·es, rach·i·des [rak, -i-deez, rey, -ki-].

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.

rachis

/ 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

rachis

/ rā′kĭs /

, Plural rachises răk′ĭ-dēz′,rā′kĭ-

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.

Derived Forms

• rachial, adjective

Other Words From

• ra·chid·i·an [r, uh, -, kid, -ee-, uh, n], ra·chi·al [rey, -kee-, uh, l], ra·chidi·al adjective

Word History and Origins

Origin of rachis¹

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

Word History and Origins

Origin of rachis¹

C17: via New Latin from Greek rhakhis ridge

Example Sentences

“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

It had a magenta rachis down the center with soft green vanes that shimmered yellow and purple and blue depending on how you turned it.

From Literature

But this specimen lacked the rachis; it just had barbs and barbules down its ribbonlike tail.

From New York Times

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

From New York Times

The finding suggests that the barbs and barbules evolved before the rachis in feathers.

From New York Times

Related Words

• bone
• vertebrae