Impaired intellectual (iq below 70) and adaptive functioning manifested during the developmental period. Use a more specific term if possible. Use for both the concept of the disorder itself and for populations of mentally retarded persons.
Subnormal intellectual functioning which originates during the developmental period; multiple potential etiologies, including genetic defects and perinatal insults; intelligence quotient (iq) scores are commonly used to determine whether an individual is mentally retarded; iq scores between 70 and 79 are in the borderline mentally retarded range and scores below 67 are in the retarded range.