Fluency is the aspect of speech production that refers to continuity, smoothness, rate, and effort. Stuttering, the most common fluency disorder, is an interruption in the flow of speaking characterized by repetitions (sounds, syllables, words, phrases), sound prolongations, blocks, interjections, and revisions, which may affect the rate and rhythm of speech. These disfluencies may be accompanied by physical tension, negative reactions, secondary behaviors, and avoidance of sounds, words, or speaking situations.
Stuttering typically has its origins in childhood. Most children who stutter, begin to do so around 2 ½ years of age. Approximately 95% of children who stutter start to do so before the age of 5 years.