Mental retardation has different levels. There is Mild intellectual disability; moderate intellectual disability; severe intellectual disability; and Profound intellectual disability.
https://www.floridahospital.com/mental-retardation-mr/symptoms-and-signs-mental-retardation
Mental retardation occurs in 2.5-3% of the general population.
In about 35% of cases, the cause of mental retardation cannot be found.
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Pseudo-retardation would be something that resembles or looks like retardation, but actually isn't. The term literally means, fake retardation.
No a dimple is not a sign of retardation.
Retardation = change in vel / time taken
The SI unit of retardation is meter per second squared or m/s^2.
There are many causes of retardation. These includes Down syndrome, velocariofacial syndrome, fetal alcohol syndrome, problems during pregnancy and other genetic disorders.
Overstudy does not cause mental retardation.
Retardation - 2015 was released on: USA: 2015
Hyperthyroidism, whooping cough, chickenpox, measles, and Hib disease (a bacterial infection) may cause mental retardation if they are not treated adequately.
Many people use it pejoratively but it is not a swear word.