stammer vs speech defect

stammer and speech defect both are nouns.

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

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

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

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

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

stammer (verb)	speech defect (verb)
speak haltingly