Overextension is the use of words in situations in which their meanings become extended or inappropriate.
It is a type of error in children's early word usage that seems to reflect an overly inclusive meaning in the mind of the child, as in referring to all four-legged animals as "doggie" or calling a round clock a moon. Likewise, Overextension refers to the young child’s tendency to use relatively specific words to refer to a broader set of objects, actions, or events than adults do, example is the use of the word car to refer to all motor vehicles. Please see also Underextension.