cramp vs myoclonus

cramp and myoclonus both are nouns.

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

As nouns, myoclonus is a hyponym of cramp; that is, myoclonus is a word with a more specific, narrower meaning than cramp:

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

cramp (verb)	myoclonus (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