Stuttering is the speech disorder where one cannot get certain syllables or words out of their mouth on the first try. They usually have to repeat the same syllable or the word a number of times before they can finally get it out. They do know what they want to speak though. Stuttering can be continuous or partial. The stutters may only come at a moment of anxiousness or fear. The underlying causes may be a psychological problem like ADHD, Autism, anxiety or a neurological problem affecting the brain-mouth co-ordination. Speech therapy exercises and anxiety reduction protocols help a lot with the problem.