Speech is the primary transmission system of language. It is divided into two subcategories: phonetics and phonology. Phonetics studies the physical properties of speech sounds and how they are produced and perceived. In contrast, phonology examines the rules which govern how sounds are organized and combined to create meaningful words.
There are many stuttering problems for people who stutter. People with an established stutter are aware of the negative effect of repetitions, prolongations, hesitations and blocks on their speech. Their stutter (stammer) may be accompanied by facial tics and uncontrolled body movements. Stuttering can lead to the avoidance of certain activities and to social isolation.