the series of vertebrae forming the axis of the skeleton and protecting the spinal cord
"the fall broke his back"
a sharp rigid animal process or appendage; as a porcupine quill or a ridge on a bone or a ray of a fish fin
"The porcupine raised its spines to defend itself from the approaching predator."
A series of bones situated at the back from the head to the pelvis of a human, or from the head to the tail of an animal, enclosing the spinal cord and providing support for the thorax and abdomen.
"The surgeon carefully examined his patient's spine after noticing severe pain radiating down the arm."
In plain English: The spine is your body's main column of bones that runs down your back and supports you upright.
"The book fell off the shelf because its spine was broken."
Usage: Use "spine" when referring specifically to the central column of vertebrae in humans and animals. Do not confuse this anatomical term with its metaphorical meaning for book bindings unless discussing physical books directly.
The word "spine" entered English in the late Middle Ages via Old French and originally referred to both a sharp plant thorn and an animal's backbone. While it retained these related meanings over time, its journey from Latin through French highlights how nature-inspired terms often describe similar structures across different contexts.