A single human vertebra.
nounpl. ver·te·brae or ver·te·bras
Origin of vertebraMiddle English, from Latin, from vertere, to turn; see wer-2 in Indo-European roots.
From Latin vertebra (“joint"), from vertere (“to turn"). Having multiple vertebrae (plural of vertebra) in one's backbone instead of having a single bone or solid spine, allows for the movement of the body with bends and turns. Hence meaning 1.