The Delphi Definition of Dyslexia Explained for Parents
Updated: Oct 28
A dyslexia report can contain unfamiliar words: phonological processing, orthographic skills, fluency and working memory. This guide explains how those ideas fit together. The starting point is the everyday difficulty: learning to read and spell, and the time or effort those activities require. The technical language should help explain that experience.
What is the Delphi definition?
The Dyslexia Delphi Study brought together researchers, assessment and education professionals, and people with lived experience to seek agreement about dyslexia. Two research papers were published in 2025. The British Dyslexia Association adopted the resulting definition. “Delphi” describes the structured method used to develop expert agreement; it is not the name of a test.
This article is a plain-English explanation, rather than the full wording of the definition or a checklist for diagnosing your child. The original definition and research are linked below.
Start with reading fluency and spelling
Think about three different questions. Can a child identify a word correctly? Can they read it with reasonable ease and pace? Can they work out and write its spelling independently? These skills overlap, but success in one does not settle the others.
The definition highlights reading fluency and spelling. For a parent, this means that a reading accuracy score alone may leave important questions unanswered.
For example, a child might finish a short passage correctly but spend so much time working through individual words that reading a chapter becomes exhausting. That example illustrates a concern to explore; it does not identify its cause.
What does processing mean here?
Processing describes what we do with information: noticing it, making sense of it, keeping relevant parts available and responding. It is too broad to be a useful explanation on its own.
Ask which skill is difficult and during which activity. A child who needs time to spell a word may be quick at explaining an idea or solving a practical problem.
Useful terms include phonological processing (working with speech sounds), orthographic skills (knowledge of written words and spelling patterns), working memory (holding information while using it), and processing speed (the pace of particular activities). These are different ideas, not interchangeable labels for being slow.
Why dyslexia looks different in different people
Imagine two pupils tackling the same homework. One spends time working out unfamiliar words; the other reads those words accurately but slowly and needs repeated spelling checks. Their visible difficulties and useful support may differ. These are illustrative situations, not separate diagnostic types or real client cases.
The definition recognises that the pattern of difficulties and their impact can vary between people and over time. An assessment explains the individual’s strengths, literacy difficulties and support needs. Dyslexia does not imply a fixed set of weaknesses, a particular talent or a particular personality.
What about age, teaching and other difficulties?
An assessor needs context. What has the young person been taught? How have reading and spelling developed? What support has been tried? Which languages do they use? What happens at home and in education? A result becomes more useful when it can be understood alongside that history.
Attention, language, coordination or maths difficulties may also be present. They deserve consideration without assuming that dyslexia explains everything. Equally, a memory difficulty alone, a family history or a difference between strong discussion and weaker writing cannot provide a diagnosis by itself.
How can parents use this information?
Bring concrete examples rather than trying to translate every difficulty into a technical label. You might say: “Reading homework takes a long time even when most words are correct”, or “Spelling is much harder when writing a sentence than when practising a short list”. Describe what helps as well as what remains difficult.
The purpose of assessment is to investigate the pattern and explain appropriate next steps. The Delphi definition does not turn one score into a yes-or-no rule. Support for a reading or spelling need should also be discussed with school while assessment is being considered.
Discussing an assessment
Mark Trewby offers diagnostic dyslexia assessments online across the UK for ages 11–21 and face-to-face in Bournemouth for ages 8–21. The £400 fee includes the assessment, personalised report within seven working days, recommendations and feedback.
Bournemouth appointments take place in a suitable client home or a hired Bournemouth library room, with Bournemouth travel and agreed room hire included.
Related dyslexia guides
Sources and further reading
More questions about the Delphi definition
These companion guides explore how family history, differences between abilities and progress after teaching fit into the wider picture. Each answers a different parent question and links back to the practical explanations above.
How dyslexia can affect learning across subjects
The definition also recognises possible effects on reading comprehension, maths and learning another language. These guides separate the different task demands and suggest useful questions for a discussion with school.
Understanding individual needs and assessment evidence
These guides explain why the impact of dyslexia varies and why an assessment needs more than one result. They connect the definition with practical questions about everyday work and interpreting a report.