Rachis

Part of speech: noun

Pronunciation: /ˈɹeɪkɪs/

Definitions

1. The main stem of a compound leaf that supports leaflets is known as the central axis, while it also refers to the shaft of a feather carrying the barbs, and it signifies the spinal column in vertebrates
2. Acting as the primary support structure of a compound leaf where leaflets branch off, this term also describes the central shaft of a feather holding barbs, as well as the backbone in animals
3. The main supporting axis from which leaflets arise in a compound leaf ; the central rod running through a feather that holds the barbs in place ; the series of vertebrae forming the backbone in animals

Etymology: The Greek word "rhákhis" originally meant "spine" or "ridge", and it was used for the backbone of animals and for any long raised ridge, such as a mountain ridge. The same image of a spine running through a structure carried over into botany and zoology, where the term now names the central stem of a leaf and the shaft of a feather. Scientists borrowed the Greek word into New Latin, the scholarly Latin used for naming discoveries in the early modern period, and the spelling "rachis" entered English through that scientific channel. Each use keeps the core idea: a single axis from which smaller parts branch off, whether those parts are leaflets, barbs, or vertebrae.