The prevalence of dyslexia is unknown, but it has been estimated to be as low as 5% and as high as 17% of the population. Dyslexia is diagnosed more often in males.

There are different definitions of dyslexia used throughout the world. Further, differences in writing systems may affect development of written language ability due to the interplay between auditory and written representations of phonemes. Dyslexia is not limited to difficulty in converting letters to sounds, and Chinese people with dyslexia may have difficulty converting Chinese characters into their meanings. The Chinese vocabulary uses logographic, monographic, non-alphabet writing where one character can represent an individual phoneme.

The phonological-processing hypothesis attempts to explain why dyslexia occurs in a wide variety of languages. Furthermore, the relationship between phonological capacity and reading appears to be influenced by orthography.