A speech disorder is when a person is unable to produce speech sounds correctly or fluently, or has problems with his or her voice. Difficulties pronouncing sounds, or articulation disorders, and stuttering are examples of speech disorders. Speech disorders can exist on their own, or be a part of another disorder, such as Autistic Spectrum Disorder or muscular dystrophy.

The term "speech disorders" can refer to many different types of speech disorders, such as:

• apraxia (a motor speech disorder where messages from the brain to the mouth are disrupted, and the person cannot move his or her lips or tongue to the right place to say sounds correctly, even though the muscles are not weak)
• dysarthria (a motor speech disorder resulting from impaired movement of the muscles used for speech production, including the lips, tongue, vocal folds, and/or diaphragm)
• stuttering (characterized by disruptions in the production of speech sounds, also called "disfluencies")
• orofacial myofunctional disorders (OMD) (the tongue moves forward in an exaggerated way during speech and/or swallowing)
• vocal cord paralysis (one or both vocal cords are unable to move)
• spasmodic dysphonia (movement of the vocal cords is forced and strained resulting in a jerky, quivery, hoarse, tight, or groaning voice)

DSM-V Classification for Common Speech Disorders

• Speech Sound Disorder F80.0
• Childhood-Onset Fluency Disorder (Stuttering) F80.81

(Definitions from the American Speech-Language-Hearing Association (ASHA)  )

• Approximately 7.5 million people in the United States have trouble using their voices.
• Between 6 and 8 million people in the United States have some form of language impairment.
• It is estimated that more than 3 million Americans stutter.
• Stuttering affects individuals of all ages but occurs most frequently in young children between the ages of 2 and 6 who are developing language.
• Most children outgrow their stuttering, and it is estimated that fewer than 1 percent of adults stutter.

(Statistics from the National Institute on Deafness and Other Communication Disorders)