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is a generalized, triarchic disorder, characterized by subaverage cognitive functioning and deficits in two or more adaptive behaviors with onset before the age of 18. Once focused almost entirely on cognition, the definition now includes both a component relating to mental functioning and one relating to the individual's functional skills in their environment. The term "mental retardation" is a diagnostic term designed to capture and standardize a group of disconnected categories of mental functioning such as "idiot", "imbecile", and "moron" derived from early IQ tests, which acquired pejorative connotations in popular discourse over time. The term "mental retardation" has itself now acquired some pejorative and shameful connotations over the last few decades due to the use of "retarded" as an insult among younger people. This may in turn have contributed to its replacement with expressions such as "mentally challenged" or "intellectual disability".