They apply a suffix to a word instead modifying the root of the word in Overregularization.
What is Overregularization?
Children frequently make mistakes when acquiring language for the first time, such as developmental errors or faults in early word use. The ability for people to learn a language is an extraordinary cognitive accomplishment. Children already exhibit general knowledge and an awareness of the fundamental linguistic patterns during the first few years of life. They are able to apply grammatical principles in new contexts and extrapolate the meaning of words they hear. Although children have a remarkable capacity to learn and understand language at a young age, they frequently make mistakes as they deepen their grasp and knowledge of language. Overgeneralization, overextension, and under extension are three common mistakes in early word use.
