The regulations for the Individuals with Disabilities Education Act (IDEA), formerly the Education of the Handicapped Act (EHA), define a learning disability as a "disorder in one or more of the basic psychological processes involved in understanding or in using spoken or written language, which may manifest itself in an imperfect ability to listen, think, speak, read, write, spell, or to do mathematical calculations."

The Federal definition further states that learning disabilities include "such conditions as perceptual disabilities, brain injury, minimal brain dysfunction, dyslexia, and developmental aphasia." According to the law, learning disabilities do not include learning problems that are primarily the result of visual, hearing, or motor disabilities; mental retardation; or environmental, cultural, or economic disadvantage. Definitions of learning disabilities also vary among states.

Having a single term to describe this category of children with disabilities reduces some of the confusion, but there are many conflicting theories about what causes learning disabilities and how many there are. The label "learning disabilities" is all-embracing; it describes a syndrome, not a specific child with specific problems. The definition assists in classifying children, not teaching them. Parents and teachers need to concentrate on the individual child. They need to observe how well the child performs, to assess strengths and weaknesses, and develop ways to help each child learn. It is important to remember that there is a high degree of interrelationship and overlapping among the areas of learning. Therefore, children with learning disabilities may exhibit a combination of characteristics.

These problems may mildly, moderately, or severely impair the learning process.

How many children have learning disabilities?
Many different estimates of the number of children with learning disabilities have appeared in the literature (ranging from 1 percent to 30 percent of the general population). In 1987, the Interagency Committee on Learning Disabilities concluded that 5 percent to 10 percent is a reasonable estimate of the percentage of persons affected by learning disabilities. The U.S. Department of Education (1995) reported that more than 4 percent of all school-aged children received special education services for learning disabilities and that in the 1993-94 school year over 2.4 million children with learning disabilities were served. Differences in estimates perhaps reflect variations in the definition.