A vertebra was an individual bone found in species with a spine; multiple vertebrae combined to make the spine and protect the spinal cord. The breaking of one or more vertebrae could often result in permanent injury or death.
In 2368, Worf was temporarily paralyzed when he was struck by falling containers of chlorinide in the USS Enterprise-D's cargo bay. Several of his vertebrae were crushed and his spinal cord was severed due to the accident. (TNG: "Ethics")
Breaking one's neck was often a loud procedure due to the noise that breaking vertebrae made. Elim Garak pointed this fact out to Quark when discussing options for Quark's requested assassination. (DS9: "Body Parts")
In 2375, The Doctor examined B'Elanna Torres and found evidence of internal bleeding, fractured vertebrae, contusions, and cranial trauma caused by B'Elanna's frequent use of the holodeck with the safety protocols disabled. (VOY: "Extreme Risk")