Communication disorders affecting speech and language can afflict children and adults. They can be the result of damage to the brain's language areas, such as when a person suffers a stroke, and affect the way words are spoken and the way they are understood.

Babies begin to understand language when they are just a few months old. By the age of 6 months, some babies understand such simple things as "no" and "bye-bye." Between the age of a year and a year-and-a-half, children can say their first words (usually "Mama" and "Dada"), follow simple instructions (such as "Come here), and even use two-word phrases such as "all gone." Although all children develop language skills at different rates (boys tend to develop them slightly later than girls do), a child who is showing no progress in language may be suffering from a communication disorder. Or, the child may...