aphonia vs speech defect

aphonia and speech defect both are nouns.

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

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

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

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