IDA 2025 Definition of Dyslexia

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“Dyslexia is a specific learning disability characterized by difficulties in word reading and/or spelling that involve accuracy, speed, or both and vary depending on the orthography. These difficulties occur along a continuum of severity and persist even with instruction that is effective for the individual’s peers. The causes of dyslexia are complex and involve combinations of genetic, neurobiological, and environmental influences that interact throughout development. Underlying difficulties with phonological and morphological processing are common but not universal, and early oral language weaknesses often foreshadow literacy challenges. Secondary consequences include reading comprehension problems and reduced reading and writing experience that can impede growth in language, knowledge, written expression, and overall academic achievement. Psychological well-being and employment opportunities also may be affected. Although identification and targeted instruction are important at any age, language and literacy support before and during the early years of education is particularly effective.”

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The International Dyslexia Association (IDA) is pleased to share the 2025 Dyslexia Definition, developed through a rigorous, collaborative process to reflect the latest research and the lived experiences of individuals with dyslexia. To explore the definition in greater depth, including the scientific and community-based foundations that informed its development, visit the 2025 IDA Definition Explanation and view the IDA Definition Presentation.