Overregularization often also known as overgeneralization takes place on both lexical and morphological level. On a lexical level, it would be overregularization on word learning. Overextension would occur while they are learning the language. Which means children would tend to generalize the meaning of the word beyond the word sense in the adult language. An example would be how all 4-legged animals can be referred to as a dog.
On a morphological level, there is both the derivational morphemes and inflectional morphomes. Overregularization is observed in derivational morphemes in forms such as how the prefix ‘un-’ can be added to many verbs to denote the reversal of an action but children often tend to overregularize this rule to yield forms such as ‘unblow’ which means deflate or ‘unlight’ which means to extinguish.
Overregularization is needless to say, commonly seen in inflectional morphemes, the regularization of the past tense marker ‘-ed’ is a very good example. As mentioned, children tend to overregularize this rule to form words such as ‘sitted’ stead of sat or ‘bringed’ instead of brought.