International Dyslexia Association
2025 Revised Definition of Dyslexia
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 genitive, 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 (IDA, 2025)
Resources available to support our understanding of the revised definition:
- 2025 Dyslexia Definition Project
- IDA 2025 Revised Dyslexia Definition Open for Public Comment (prior to the IDA Board’s adoption of the definition on October 22, 2025; document links discussing the development process )
- IDA 2025 Conference Handout: 2025 Revised Dyslexia Definition – Explanatory Document
- Understanding the Dyslexia Definition from Tim Odegard
- Understanding the Revised Dyslexia Definition; Companion Guide from Tim Odegard
2025-11-8 Ruth Harris Symposium Presentation on the Revised Dyslexia Definition