myalgia vs pain

myalgia and pain both are nouns.

Word	Noun	Adjective	Verb	Adverb
myalgia	Yes	No	No	No
pain	Yes	No	Yes	No

As nouns, pain is a hypernym of myalgia; that is, pain is a word with a broader meaning than myalgia:

Other hypernyms of myalgia include hurting.

myalgia (noun)	pain (noun)
pain in a muscle or group of muscles	a somatic sensation of acute discomfort
	something or someone that causes trouble; a source of unhappiness
	emotional distress; a fundamental feeling that people try to avoid
	a symptom of some physical hurt or disorder

myalgia (verb)	pain (verb)
	cause bodily suffering to and make sick or indisposed
	cause emotional anguish or make miserable