- Slowness or limitation of development.- mental r. subaverage general intellectual functioning that originates during the developmental period and is associated with impairment in adaptive behavior. The American Association on Mental Deficiency lists eight medical classifications and five psychologic classifications; the latter five replace the three former classifications of moron, imbecile, and idiot. Mental r. classification requires assignment of an index for performance relative to a person's peers on two interrelated criteria: measured intelligence (IQ) and overall socioadaptive behavior (a judgmental rating of the individual's relative level of performance in school, at work, at home, and in the community). In general an IQ of 70 or below indicates mental r. (mild = 50/55–70; moderate = 35/40–50/55; severe = 20/25–35/40; profound = below 20/25); an IQ of 70–85 signifies borderline intellectual functioning. SYN: amentia (1), mental deficiency, oligophrenia.- viscoelastic r. a technique for the measurement of the molecular weight of large DNA molecules; the DNA is stretched by hydrodynamic shear forces and, when the molecules relax, the relaxation time is measured.
* * *re·tar·da·tion .rē-.tär-'dā-shən, ri- n2) slowness in development or progress
* * *n.the slowing up of a process. Psychomotor retardation is a marked slowing down of activity and speech, which can reach a degree where a patient can no longer care for himself. It is a symptom of severe depression. The term mental retardation implies a delay in intellectual development rather than a qualitative defect.
* * *re·tar·da·tion (re″tahr-daґshən) [L. retardare to slow down, impede] delay; hindrance; delayed development.
Medical dictionary. 2011.