Rachis
Part of speech: noun
Definition: The main shaft of either a compound leaf, head of grain, or fern frond. The spine or the vertebrae of the spine. The central shaft of a feather.
Spine
Part of speech: noun
Definition: A person or thing's backbone; the series of bones collectively from one's (literal or figurative) head to tail or pelvis.A rigid, pointed surface protuberance or needle-like structure on an animal, shell, or plant.Courage or assertiveness.The narrow, bound edge of a book.
Example sentence: A great number of the women are victims to falling of the womb and weakness in the spine; but these are necessary results of their laborious existence, and do not belong either to climate or constitution.