stammer vs defect of speech

stammer and defect of speech both are nouns.

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

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

stammer: a speech disorder involving hesitations and involuntary repetitions of certain sounds
defect of speech: a disorder of oral speech

Other hypernyms of stammer include speech defect, speech disorder.

stammer (noun)	defect of speech (noun)
a speech disorder involving hesitations and involuntary repetitions of certain sounds	a disorder of oral speech

stammer (verb)	defect of speech (verb)
speak haltingly