free nerve ending vs nerve end

free nerve ending and nerve end both are nouns.

Word	Noun	Adjective	Verb	Adverb
free nerve ending	Yes	No	No	No
nerve end	Yes	No	No	No

As nouns, nerve end is a hypernym of free nerve ending; that is, nerve end is a word with a broader meaning than free nerve ending:

free nerve ending: microscopic sensory nerve endings in the skin that are not connected to any specific sensory receptor
nerve end: the terminal structure of an axon that does not end at a synapse

Other hypernyms of free nerve ending include nerve ending.

free nerve ending (noun)	nerve end (noun)
microscopic sensory nerve endings in the skin that are not connected to any specific sensory receptor	the terminal structure of an axon that does not end at a synapse