More than 6% of all adults in the United States have speech difficulties that involve articulation, language, voice, fluency, hearing, or swallowing. In addition, 5% of all children exhibit impaired speech, language, or hearing. Many of these individuals can be helped by speech therapy.

Speech and language disorders affect the way people speak to and understand each other. These disorders may range from problems with simple sounds to not being able to speak or use language at all. Speech and language disorders include stuttering, characterized by interruptions in the regular flow or rhythm of speech; articulation disorders, involving difficulties in forming or stringing sounds together; voice disorders, characterized by inappropriate voice pitch, loudness, or quality; aphasia, or the loss of speech and language abilities resulting from stroke or head injury; and delayed language disorder, characterized by slow development of the vocabulary and grammar required to express and understand...