dysarthria vs defect of speech

dysarthria and defect of speech both are nouns.

Word	Noun	Adjective	Verb	Adverb
dysarthria	Yes	No	No	No
defect of speech	Yes	No	No	No

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

dysarthria: impaired articulatory ability resulting from defects in the peripheral motor nerves or in the speech musculature
defect of speech: a disorder of oral speech

Other hypernyms of dysarthria include speech defect, speech disorder.

dysarthria (noun)	defect of speech (noun)
impaired articulatory ability resulting from defects in the peripheral motor nerves or in the speech musculature	a disorder of oral speech