Retardation is the process of making something happen or develop more slowly, or the fact of being less well developed than other people or things of the same kind.
[formal]
...other parents whose children had mental retardation.
retardation in British English
(ˌriːtɑːˈdeɪʃən) or less commonly retardment (rɪˈtɑːdmənt)
noun
1.
the act of retarding or the state of being retarded
2.
something that retards; hindrance
3.
the rate of deceleration
Derived forms
retardative (reˈtardative) or retardatory (reˈtardatory)
adjective
retardation in American English
(ˌritɑːrˈdeiʃən)
noun
1.
the act of retarding or state of being retarded
2.
something that retards; hindrance
3. often offensive
slowness or limitation in intellectual understanding and awareness, emotional development, academic progress, etc
4. Music
a form of suspension that is resolved upward
Also: retardment
Derived forms
retardative (rɪˈtɑːrdətɪv) or retardatory (rɪˈtɑːrdəˌtɔri, -ˌtouri)
adjective
Word origin
[1400–50; late ME retardacioun ‹ L retardātiōn- (s. of retardātiō), equiv. to retardāt(us) ( see retard, -ate1) + -iōn--ion]