Vertebrae
Vertebrae are the bones that form the spine. The singular word is vertebra. Together, these bones provide support and form a protective passage for the spinal cord and nerves.
In everyday words
A label such as L4 identifies a vertebra in the lumbar, or lower-back, region. The letter names the region and the number identifies the level.
What to keep in mind
Vertebrae are bones; the disks between many of them are different structures. A scan report may discuss both, so ask your clinician to explain unfamiliar wording in context.