Human Phenotype Ontology term HP_0001249 (Intellectual disability) can be described as follows. The term intellectual disability or intellectual developmental disorder is used to describe significantly sub-average intellectual and adaptive functioning based on clinical assessment and as measured by individually administered, appropriately normed, standardized and validated tests of intellectual functioning and adaptive behavior, with onset during the developmental period from infancy through adolescence. Also known as: Mental deficiency, Mental retardation, Mental retardation, nonspecific, Mental-retardation, Nonprogressive intellectual disability, Nonprogressive mental retardation.