The American Association on Intellectual and Developmental Disabilities (AAIDD) has published the 11th edition of the definition manual: Intellectual Disability: Definition, Classification, and Systems of Supports. In it, the AAIDD sets forth "practice guidelines on diagnosing and classifying intellectual disability and developing a system of supports for people living with an intellectual disability." At the center of the organization's philosophy is an effort to abolish the stigma of intellectual disabilities: specifically by removing "mental retardation" from medical lexicon.
In related news, senators Barbara Mikulski of Maryland and Michael Enzi of Wyoming have introduced a bipartisan bill entitled "Rosa's Law," which would replace "mental retardation" with "intellectual disability" in the federal law books. Rosa's Law has gathered 28 co-sponsors so far. You can track the bill's progress at govtrack.us.