dorsal root vs afferent nerve

dorsal root and afferent nerve both are nouns.

Word	Noun	Adjective	Verb	Adverb
dorsal root	Yes	No	No	No
afferent nerve	Yes	No	No	No

As nouns, afferent nerve is a hypernym of dorsal root; that is, afferent nerve is a word with a broader meaning than dorsal root:

dorsal root: one of two roots of a spinal nerve that passes dorsally from the spinal cord and that consists of sensory fibers
afferent nerve: a nerve that passes impulses from receptors toward or to the central nervous system

Other hypernyms of dorsal root include afferent, sensory nerve.

dorsal root (noun)	afferent nerve (noun)
one of two roots of a spinal nerve that passes dorsally from the spinal cord and that consists of sensory fibers	a nerve that passes impulses from receptors toward or to the central nervous system