For more than twenty years, one definition shaped how we talked about dyslexia. The 2002 International Dyslexia Association (IDA) definition found its way into state laws, district handbooks, evaluation reports, and countless parent conferences. On October 22, 2025, the IDA Board of Directors adopted a revised definition built on two decades of research.
I had the privilege of serving on the steering committee that developed the new definition. Since its release, the question I hear most from teachers and administrators is simple: What actually changes for us?
Definitions matter because they travel. The words we choose end up in statutes, eligibility decisions, and the conversations we have with families at the kitchen table. When the wording shifts, practice should shift with it. You can read the full 2025 definition on IDA’s website and the scientific rationale in Catts, Haynes, and Joshi (2026) in Annals of Dyslexia.
What Changed: 2002 vs. 2025
The new definition keeps dyslexia anchored as a specific learning disability, the category used in IDEA. What changes is how we describe its nature, its causes, and its reach.
| Element | 2002 Definition | 2025 Definition |
|---|---|---|
| Core difficulty | Accurate and/or fluent word recognition; poor spelling and decoding | Word reading and/or spelling, involving accuracy, speed, or both; varies by writing system |
| Severity | Not addressed; often treated as binary: yes/no | Occurs along a continuum of severity |
| Causes | Neurobiological in origin | Genetic, neurobiological, and environmental influences interacting over development |
| Underlying processes | A deficit in phonological processing | Phonological and morphological difficulties are common but not universal; early oral language weaknesses are often a warning sign |
| Basis for identification | Relative to other cognitive abilities and effective classroom instruction | Cognitive-ability comparison removed; difficulties persist despite instruction that works for peers |
| Secondary consequences | Comprehension, vocabulary, background knowledge | Adds written expression, academic achievement, psychological well-being, and employment |
| Timing of support | Not addressed | Important at any age; especially effective before and during the early school years |
The removal of the cognitive-ability comparison deserves emphasis. Students across the full range of cognitive profiles can have dyslexia, so an IQ–achievement discrepancy has no place in identification.
What Has Not Changed
Dyslexia remains a specific learning disability that primarily affects word reading and spelling. Students still need explicit, systematic instruction based on their individual needs. The revised definition does not minimize the importance of phonological processing or decoding. Instead, it broadens our understanding of dyslexia by recognizing that no single underlying weakness explains every student’s reading and spelling difficulties.
What This Does Not Mean for Identification
The revised definition is not an identification checklist or a diagnostic formula. No single test score, cognitive profile, phonological weakness, or cutoff determines whether a student has dyslexia. Identification still requires teams to consider multiple sources of data, the student’s response to effective instruction, developmental history, and patterns of reading and spelling performance.
Unpacking the Key Language
Screening
Accuracy, speed, or both: The 2002 definition used “fluent”; the new one names speed directly. Some students read words correctly but laboriously, and they need our attention just as much as students who misread. Screeners should capture both dimensions.
Common but not universal: Phonological weaknesses are typical, but a strong phonemic awareness score does not rule dyslexia out. Early screening should also look at letter-sound knowledge, rapid naming, vocabulary, and oral language, since early language weaknesses often foreshadow literacy challenges.
Language difference still matters: Reading and spelling data must also be interpreted within a student’s linguistic context. Multilingual students and students who speak language varieties such as African American English may demonstrate patterns that reflect language difference rather than disability. The revised definition reinforces the need to examine multiple sources of evidence rather than interpreting an isolated language or literacy feature as evidence of dyslexia.
Intervention
A continuum of severity: Dyslexia is not an on/off switch or a yes/no. Dyslexia occurs on a continuum (e.g., mild, moderate, severe and levels in between). Intervention intensity, including dosage, group size, and explicitness, should scale with need rather than wait on a label.
Persists even with effective instruction: Persistence is judged against instruction that works for a student’s peers. That means we need evidence that core instruction is effective, and it is never a reason to wait. Support begins at the first sign of risk.
Family Communication
The new language gives us words families can hear. Dyslexia is not about intelligence or effort. It varies from mild to severe, it responds to targeted instruction, and it can affect confidence and well-being.
For Administrators: Aligning Policy
Many state laws and district handbooks still use 2002 wording. Until they are revised, leaders must follow current statute while bringing local practice in line with the research. Some ways to do this include:
- Audit local documents for language that ties dyslexia to a single cause, treats it as unexpected relative to cognitive ability, or implies an IQ–achievement discrepancy.
- Review screening tools to confirm they measure both accuracy and speed, include oral language, and account for students’ language backgrounds.
- Build decision rules that match intervention intensity to severity instead of waiting for a formal label.
- Document core instruction so teams can judge whether difficulties persist despite instruction that works for peers.
- Update family materials so letters, notices, and meeting scripts reflect the new language.
For Teachers: Strategies for Monday Morning
Teachers will leave with instructional moves they can use right away; each tied to a specific part of the definition:
- Teach morphology explicitly: The revised definition recognizes that morphological processing difficulties, like phonological difficulties, are common but not universal. Teach students how prefixes, suffixes, bases, and roots contribute to word meaning, pronunciation, and spelling.
- Read spelling as data: A student’s misspellings reveal what they know about sounds, letter patterns, and meaningful word parts. Use them to target instruction rather than simply marking errors.
- Build accuracy, then speed: Secure accurate decoding first, then build automaticity through repeated practice with words and connected text.
- Incorporate oral language across all grade levels: Vocabulary, sentence work, and rich talk strengthen the foundation that early literacy rests on.
- Protect access and confidence: Audiobooks and read-alouds keep knowledge growing while decoding develops. Noticing frustration and naming strengths matters, since well-being is now part of the definition.
The Bottom Line
The 2025 definition moves us away from searching for one defining cause or one test score. Instead, it asks us to recognize dyslexia as a developmental difficulty that varies in severity, can involve multiple underlying processes, and must be understood in the context of instruction and the individual learner. For schools, the message is straightforward: identify risk early, provide effective instruction, examine patterns across multiple sources of data, and intensify support according to need.
References
Catts, H. W., Haynes, C. W., & Joshi, R. M. (2026). Defining dyslexia: 2025 revision. Annals of Dyslexia.
International Dyslexia Association. Definition of Dyslexia (adopted October 22, 2025).
