Dyslexia as defined by IDA:
“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.”
Adopted by the IDA Board of Directors on October 22, 2025. For more detailed context, please visit the 2025 IDA Definition Explanation, which includes the IDA Definition Presentation. The 2002 Definition Consensus Project remains available as a historical reference.
Individuals who experience difficulty with the following may be associated with dyslexia:
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- Learning to speak
- Pronouncing words
- Learning letters and sounds
- Slow to add new vocabulary words
- Learning to rhyme
- Computing math problems correctly
- Memorizing math facts
- Learning to tell time
- Make consistent reading and spelling errors: letter reversals, word reversals, inversions, transpositions, and substitutions
- Unable to follow multi-step directions or routines
- Organizing spoken and written language
- Often uses an awkward pencil grip
- Poor fine motor coordination
- Learning a foreign language
- Comprehending the written word due to a slow reading rate
Dyslexia is Real: Common Facts
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- Dyslexia is the most common learning disability.
- Scientists and researchers estimate that up to 20% of the population has dyslexia.
- Dyslexia affects boys and girls equally.
- The causes of dyslexia are neurological and genetic.
- People with dyslexia tend to have average to above-average intelligence.
- There is no cure for dyslexia. It is a lifelong condition.
- Dyslexia is not a vision problem.
Illinois State Board of Education – Dyslexia Guide & Toolkit
The purpose of the Dyslexia Handbook is to provide information and guidance for educational professionals, school leaders, families, guardians, and students themselves on the subject of dyslexia.
The Dyslexia Toolkit provides evidence-based assessment and curricular materials focused on learners with dyslexia, those with other specific learning disabilities, as well as students who struggle with reading. The toolkit includes websites, books, videos, podcasts, screeners, training opportunities, and additional reading materials, catering to diverse target audiences.
(SOURCE: SLDSupports.org)
