aphonia vs speech disorder

aphonia and speech disorder both are nouns.

Word	Noun	Adjective	Verb	Adverb
aphonia	Yes	No	No	No
speech disorder	Yes	No	No	No

As nouns, speech disorder is a hypernym of aphonia; that is, speech disorder is a word with a broader meaning than aphonia:

Other hypernyms of aphonia include defect of speech, speech defect.

aphonia (noun)	speech disorder (noun)
a disorder of the vocal organs that results in the loss of voice	a disorder of oral speech