Spinal Nerves: arise from segments of the "spinal cord." Each segment gives rise to both sensory and motor nerve ‘roots’ on each side of the body. (Blumenfeld, 22)

Each spinal nerve emanates from the spinal cord as dorsal and ventral ‘rootlets.’ (Patestas, 55) Functionally equivalent to the “cranial nerves.” Whereas the cranial nerves receive information from sensory receptors in the eyes, ears, facial skin, and so forth, the spinal nerves receive information from sensory receptors in the rest of the body. (Kolb, 59) Editor's note - includes the ‘cervical nerves,’ the ‘lumbar nerves,’ the ‘sacral nerves,’ and the ‘thoracic nerves.’

Spinal Nerve Root: fibers collect together as they enter (or exit) the spinal cord and so form a (nerve) root. (Kolb, 58) Arises from each segment of the spinal cord. (Blumenfeld, 321) One of the two bundles of nerve fibers (dorsal and ventral roots) emerging from the spinal cord that join to form each spinal nerve. (NCIt) The paired bundles of nerve fibers entering and leaving the spinal cord at each (“spinal segment”). The dorsal and ventral nerve roots join to form the mixed segmental spinal nerves. The dorsal roots are generally “afferent,” formed by the central projections of the sensory cells, and the ventral roots “efferent,” comprising the axons of spinal motor and autonomic neurons. There are, however, some exceptions to this afferent/efferent rule. (MeSH) Also referred to as ‘spinal root.’

Dorsal Roots: convey mainly “afferent” sensory information into the dorsal spinal cord. (Blumenfeld, 22) Also referred to as ‘dorsal nerve roots.’

Dorsal Rootlets: composed of (axons) of a large number of neurons. Emanate from a “spinal nerve.” Join and enter the dorsal root “ganglion” housing nerve cell bodies (of sensory neurons.) (Patestas, 56)

Ventral Roots: carry mainly “efferent”  “motor”  “signals” from the ventral spinal cord to the periphery. (Blumenfeld, 22) Also referred to as ‘ventral nerve roots.’

Ventral Rootlets: join to form a single ventral root, housing the axons of “motor neurons.” (Patestas, 56)