The less severe cases can be fairly common, but tend to either fix themselves or be fixed by low intensity therapy.  More severe cases can persist through adulthood. Speech and language disorders refer to problems in communication and related areas. These delays and disorders range from substitutions of a different sound for the correct one to the inability to understand or use language for functional speech. Some causes of speech and language disorders include hearing loss, neurological disorders, brain injury, mental retardation, drug abuse, physical impairments (such as cleft lip or palate), and vocal abuse or misuse. Frequently, however, the cause is unknown.  Language disorders may be related to other disabilities such as mental retardation, autism or cerebral palsy.

• There are expected language behaviors for different ages.  By 1 year of age a child should use one or two words, follow simple requests ("Come here"), and understand simple questions ("Where's your shoe?"). By 2 - 3 years of age, the child should be using two or three word sentences to talk about and ask for things and following two requests ("Get the ball and put it on the table"). Parents should also understand their child's speech most of the time.
• Children are individuals and do develop at slower or faster rates than expected. What is most important is that the child shows continuous language growth.