Retardation is the act or result of delaying; the extent to which anything is retarded or delayed; that which retards or delays.
Retardation or retarded or similar may refer to:
Medicine and biology
Mental retardation, also known as intellectual disability, a disorder characterized by significantly impaired cognitive functioning and deficits in adaptive behaviors
Psychomotor retardation, a slowing-down of thought and a reduction of physical movements in an individual
A form of heterochrony, able to cause effects such as neoteny, retention by adults of traits previously seen only in the young