myoclonus vs cramp

myoclonus and cramp both are nouns.

Word	Noun	Adjective	Verb	Adverb
myoclonus	Yes	No	No	No
cramp	Yes	No	Yes	No

As nouns, cramp is a hypernym of myoclonus; that is, cramp is a word with a broader meaning than myoclonus:

Other hypernyms of myoclonus include muscle spasm, spasm.

myoclonus (noun)	cramp (noun)
a clonic spasm of a muscle or muscle group	a strip of metal with ends bent at right angles; used to hold masonry together
	a clamp for holding pieces of wood together while they are glued
	a painful and involuntary muscular contraction

myoclonus (verb)	cramp (verb)
	suffer from sudden painful contraction of a muscle
	affect with or as if with a cramp
	prevent the progress or free movement of
	secure with a cramp