rachis

Definitions

1. The spinal column, or the vertebrae of the spine.
   obsolete
2. An anatomical shaft or axis in a marine invertebrate.
3. The central shaft of a feather.
4. The axis of either a compound leaf, inflorescence, or fern frond.

Equivalents

Examples

“In some squid species, the pen rachis flares out into wings on either side, and the tip⟳ of the rachis grows into a thick cone.”

CEFR level