Rhachis
/ˈreɪ.kɪs/noun
The central axis or spine of a structure, especially a feather, leaf, or cluster.
Did you know?In Greek anatomy, *rháchis* was literally the “spine” or “ridge,” and that same ancient image still survives in scientific words for the central axis of living things.
Etymological Timeline
Ancient Greek
Greek
ῥάχις (rháchis)
“spine, backbone, ridge, central axis”
Late Latin
Latin
rachis
“spine, ridge; central supporting axis”
14th Century
English
rachis
“the spine or backbone; later, the central axis of a feather or plant”
Modern English
English
rachis
“the main axis or “stem” of a compound structure, especially in botany or anatomy”