Mental retardation, also called intellectual or developmental disability, is a medical condition where a person shows limited learning and functioning abilities compared to others in the same age group. Diagnosed before the age of 18, individuals with mental retardation show a below-average intellectual function and lack skills needed for daily living.
Infants and toddlers show different levels of learning, motor development, and language skills. Mental retardation is often diagnosed when a child is in the elementary school level, mostly within the first two to three grades. Based on its stages, mental retardation has been classified in to mild, moderate, severe and profound.