It is a specific partial disorder of the reading function, caused by the lack of development of higher psychiatric functions and manifested in constantly repeated mistakes; partial disorder manifests itself in the process of reading acquisition in the form of substitutes, and rearrangement, and omission of letters.

Dyslexia is often accompanied by phonetic distortions and incorrect understanding of simple text. Severe cases of the disorder manifest as dyslexia (see dyslexia).