Definition of Dyslexia
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 Definition Explained: 2025 Dyslexia Definition Project.
In October 2025, IDA adopted this updated 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 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.
https://dyslexiaida.org/definition-of-dyslexia/
Understanding the Updated IDA Dyslexia Definition
New infographic! National Center on Improving Literacy. (2026). Understanding the New IDA Dyslexia Definition. https://improvingliteracy.org/resource/understanding-the-new-ida-dyslexia-definition/
Dyslexia Defined: Unpacking the 2025 IDA Definition
Recording Available – EdWeb hosted Tim Odegard, Ph.D., Professor of Psychology and Chairholder, Chair of Dyslexic Studies, Middle Tennessee State University ( 1/28/2026)
Understanding the Revised Definition of Dyslexia
Dr. Odegard, Katherine Davis Murfree Chair of Excellence in Dyslexic Studies and Professor of Psychology at MTSU, has authored two new documents to help practitioners, parents, and policymakers unpack and understand the IDA’s 2025 revised definition of dyslexia. As a member of the Steering Committee, Dr. Odegard played an instrumental role in crafting the 2025 definition.
Tennessee Center for the Study and Treatment of Dyslexia, 2025
Infographic (at a glance)
Companion Guide (full)
The Southern Region Branches of IDA (AL, FL, GA, LA, NC, SC, TN) hosted a free webinar on December 10, 2025 featuring Dr. Charley Haynes and Dr. Hugh Catts. Watch the recording to learn about the new definition of dyslexia and the reasoning behind the decisions.
Recording: The recording is housed on IDA Georgia’s YouTube Channel.
Slide Deck: The link to the most comprehensive version of the slides is on IDA’s website, below the definition: https://dyslexiaida.org/2025-dyslexia-definition-project/
Statement: EXPLANATION of IDA’s 2025 Updated Definition of Dyslexia
Other Resources Mentioned During the Webinar:
EdWeek Webinar: Bringing Dyslexia Screening into the Future
Snowling & Hulme (2025), Risk Factors for Dyslexia: Addressing Oral Language Deficits
Share (2025), Blueprint for a Universal Theory of Learning to Read: The Combinatorial Model