For more than two decades, the International Dyslexia Association’s (IDA) working definition of “dyslexia” has helped shape research, policy, and classroom practice around the world. In 2025, the organization released the first major revision since 2002. The updated definition reflects advances in reading science, a deeper understanding of how dyslexia develops and manifests across learners, and the evolving needs of today’s educators and students.
This update, described in more detail in the IDA’s article “Defining dyslexia: 2025 revision,” is significant, and it’s important to understand what it does—and doesn’t—mean. This change does not shift who is identified with dyslexia, nor does it ignore the students who continually struggle to learn to read. Instead, it updates the language used to describe dyslexia so it better reflects what decades of research have taught us about reading development, effective instruction, and the many ways dyslexia can present across individuals and languages.
For educators, this matters. Whether you’re a classroom teacher, reading specialist, school or district administrator, or interventionist, the updated definition has implications for how schools think about screening, instruction, intervention, and identification. It also has implications for families and caregivers seeking answers, students working to understand their own learning, and systems such as multi-tiered systems of support (MTSS), where early identification and evidence-based instruction are foundational to student success.
At NWEA, we see our role as helping educators bridge the gap between research and practice. We aim to help educators understand what new evidence means for teaching and learning as literacy research continues to evolve. We’ve explored common misconceptions in “Unraveling dyslexia: Dispelling myths and understanding early intervention,” answered frequently asked questions in “9 common questions about dyslexia, answered,” and examined how effective screening and intervention fit within an MTSS framework in “MTSS in action: A dyslexia specialist weighs in on screening, support, and success.” Together, these resources help translate reading science into practical classroom decisions.
In this article, I’ll explain the IDA’s updated 2025 definition of “dyslexia,” why it was revised, what changed, and what it means for educators, all while distinguishing the definition itself from the broader research that informs instructional practice.
What is dyslexia? The International Dyslexia Association’s 2025 definition
The IDA’s 2025 definition of “dyslexia” builds on the organization’s 2002 working definition while reflecting current research on how dyslexia develops, how it presents across different languages and learners, and why early identification and intervention matter.
The complete definition is as follows: “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.”
Like with any comprehensive definition, there’s a lot to unpack. Here’s what the updated definition emphasizes.
- Dyslexia is a specific learning disability. The updated definition reaffirms that dyslexia is a specific learning disability affecting word reading and spelling. It is not a reflection of intelligence, motivation, or effort. The update reinforces the importance of accurate identification and appropriate support.
- Persistent word-reading and spelling difficulties are the defining characteristics. Dyslexia primarily affects accurate and/or fluent word reading and spelling. Reading comprehension challenges may occur but are generally a consequence of word-reading difficulties rather than the defining feature of dyslexia.
- Dyslexia exists on a continuum. The IDA’s revised definition recognizes that dyslexia varies in severity and presentation. There is no single profile that describes every learner with dyslexia.
- Difficulties persist despite effective instruction. Dyslexia is characterized by reading and spelling difficulties that continue despite instruction that is effective for most peers. This distinction helps differentiate dyslexia from reading difficulties primarily caused by inadequate instruction while reinforcing the need for timely intervention.
- Dyslexia has multiple interacting causes. Rather than attributing dyslexia solely to neurobiology, the definition reflects current research showing that genetic, neurobiological, and environmental factors interact over time to influence its development.
- Phonological processing remains important but is not the whole story. Difficulties with phonological processing remain a key characteristic of dyslexia, but the updated definition recognizes that they are part of a broader and more complex developmental picture.
- Dyslexia can have lifelong consequences. Beyond word reading and spelling, dyslexia can affect vocabulary, writing, academic achievement, psychological well-being, and later educational and employment opportunities if appropriate support is not available.
- Early identification and intervention matter. The definition emphasizes that support is beneficial at any age but is most effective when provided early through evidence-based screening, instruction, and intervention.
Why did the International Dyslexia Association update the definition of “dyslexia”?
The short answer is that our understanding of dyslexia has evolved.
The IDA’s 2002 working definition established a shared understanding of dyslexia for researchers, educators, specialists, and policymakers. Since then, advances in reading science have expanded our understanding of how dyslexia develops, how it presents across languages and writing systems, and the importance of early identification and intervention.
To reflect this growing body of evidence, the IDA convened an international steering committee and engaged researchers, educators, clinicians, advocates, individuals with dyslexia, and family members in a multiyear revision process. The goal was not to redefine “dyslexia” but to update the definition to reflect current research and lived experience.
The 2025 definition uses more precise, inclusive language that reflects current scientific understanding of dyslexia. Rather than changing the fundamental nature of the disability, it provides educators, families, and schools with a clearer, more research-informed framework for supporting individuals with dyslexia.
What has changed in the 2025 “dyslexia” definition?
The updated definition doesn’t change what dyslexia is, but it does reflect advances in research and educational practice. Rather than redefining “dyslexia,” it provides a more complete framework for understanding its characteristics, causes, and implications for learning.
The revised definition recognizes that dyslexia exists on a continuum and can present differently across learners, languages, and writing systems. It also reflects current understanding that dyslexia develops through the interaction of multiple genetic, neurobiological, and environmental influences.
Another notable shift is its emphasis on action. The definition highlights the importance of early identification, evidence-based instruction, and timely intervention while acknowledging that dyslexia can affect academic achievement and well-being throughout a person’s life.
Overall, the update aligns the definition with current reading science and provides educators, families, and schools with a clearer, more research-informed understanding of dyslexia.
How does the 2025 “dyslexia” definition reflect current reading science?
The updated definition reflects decades of research on how reading develops and why some students continue to experience reading difficulties despite effective instruction. It aligns with current reading science by recognizing that dyslexia develops through multiple interacting influences and often involves difficulties with the language skills that support accurate and fluent word reading.
The definition also reinforces a central message of reading science: early identification, evidence-based instruction, and timely intervention improve outcomes for students with dyslexia.
How can dyslexia vary across learners and co-occur with other learning differences?
No two learners with dyslexia experience it in exactly the same way. The nature and severity of reading and spelling difficulties can vary across individuals, ages, languages, and learning environments. Some students may primarily struggle with accurate word reading, while others experience greater challenges with reading fluency, spelling, or a combination of these skills.
Dyslexia may also co-occur with other learning differences, such as attention-deficit/hyperactivity disorder (ADHD), developmental language disorder (DLD), or dysgraphia. While these conditions can influence how dyslexia presents, dyslexia remains a distinct and identifiable learning disability that requires targeted, evidence-based support.
What is the importance of early identification, screening, and intervention in dyslexia outcomes?
Research, including the articles “Early identification and interventions for dyslexia: A contemporary view” and “Forty years of reading intervention research for elementary students with or at risk for dyslexia: A systematic review and meta-analysis,” consistently shows that early identification and intervention improve outcomes for students with dyslexia. Universal screening helps identify students at risk before reading difficulties become more severe, allowing schools to provide timely, evidence-based instruction. This emphasis on early action is reflected throughout the IDA’s updated definition and aligns with multi-tiered systems of support (MTSS), where educators use screening, progress monitoring, and student response to guide instruction.
To support early identification, MAP® Reading Fluency™ includes a dyslexia screener that helps educators identify students who may be at risk for dyslexia and determine who may benefit from additional evaluation or intervention. To learn more about how the screener works and how it supports schools, read “5 things to know about the new MAP Reading Fluency dyslexia screener.”
What does the 2025 “dyslexia” definition mean for educators and schools?
For educators, the updated definition reinforces that dyslexia should be understood within the broader context of evidence-based literacy instruction and a multi-tiered system of support (MTSS). Rather than advocating for changes in how students are taught to read, the revised definition provides clearer language about the characteristics of dyslexia and the cognitive processes that contribute to reading and spelling difficulties. This shared understanding can help educators recognize students who may need additional support and guide conversations about screening, instruction, intervention, and progress monitoring.
The revised definition also highlights the importance of early identification. Universal screening, ongoing assessment, and timely intervention remain essential for preventing reading difficulties from becoming more severe. While a dyslexia diagnosis is not required to provide effective reading instruction, students with characteristics of dyslexia benefit from explicit, systematic, cumulative instruction in foundational reading skills, including phonemic awareness, phonics, decoding, spelling, fluency, vocabulary, and comprehension.
For schools and districts, the updated definition offers a common framework for professional learning, consistent communication, and literacy policies aligned with the science of reading. Ultimately, it helps education systems make more informed decisions about screening, instruction, and intervention to improve outcomes for students with dyslexia.
What does the 2025 “dyslexia” definition mean for families and students?
The updated definition gives families and educators a clearer, research-based understanding of dyslexia. Using accessible language, it explains what dyslexia is, why early identification matters, and how evidence-based instruction can support students. This shared understanding can help families advocate for their children and partner with schools to provide appropriate support.
The revised definition also reinforces that dyslexia is not a reflection of intelligence, motivation, or effort. Recognizing this can reduce stigma, build student confidence, and help families and educators work together to support reading development and long-term success.
What are the implications for education policy, advocacy, and systems change?
A shared, research-informed definition of “dyslexia” has implications beyond individual classrooms. As states, districts, and organizations update literacy initiatives, screening practices, educator preparation, and related policies, the revised IDA definition provides a common language for understanding dyslexia and supporting students consistently across education systems. For those involved in education governance, including school board members, it also provides a stronger foundation for developing, interpreting, and implementing policies that support evidence-based literacy practices and early intervention.
The updated definition can also inform future policy and legislation related to dyslexia identification, evidence-based reading instruction, and access to intervention. Although policies vary by state and country, aligning them with current research can help ensure students receive timely support and educators have the tools and professional learning needed to meet diverse literacy needs.
For advocates, the revised definition strengthens conversations with policymakers, school leaders, and communities about early identification, effective instruction, and equitable access to support. Ultimately, the goal is not simply to update terminology but to improve outcomes for students through coordinated, evidence-based literacy systems.
How can stakeholders provide input on the International Dyslexia Association’s “dyslexia” definition?
The IDA’s 2025 revisions are final, but because the definition is intended to guide research, education, clinical practice, and policy, the IDA invited public feedback before finalizing it. During the public comment period, educators, families, researchers, clinicians, advocates, and individuals with dyslexia were encouraged to review the proposed definition and share their perspectives. The goal was to ensure the final definition reflects both the latest scientific evidence and the lived experiences of those it affects.
To learn more about the IDA’s process, see “Revisiting the definition of ‘dyslexia’: An international, evidence-based update for the 21st century.”
Key takeaways from the 2025 “dyslexia” definition update
The IDA’s 2025 definition reflects advances in reading science while reinforcing what research has long shown: dyslexia is a specific learning disability that requires early identification, evidence-based instruction, and timely intervention.
For educators, the update reinforces that dyslexia can present differently across learners, that persistent reading difficulties warrant targeted support, and that high-quality instruction and screening remain essential. While the language has evolved, the focus remains on helping schools identify students early and provide the evidence-based support that leads to stronger reading outcomes.
