The Delphi Definition of Dyslexia: What It Means for Children and Adults

Dyslexia Testing

If you have been reading about dyslexia, you may have come across the Delphi definition published in 2025. But what does it mean for you or your child?

Professional definitions can sound quite technical. Their value lies in helping us understand difficulties more clearly and guiding careful assessment.

For me, the important question is how that understanding helps the person. Does it explain their experiences? Does it help the people around them provide appropriate support? And does it challenge the belief that finding something difficult means they are not trying hard enough?

What is the Delphi definition of dyslexia?

The definition emerged from a structured process of consultation with experts. The Delphi method involves gathering and refining expert views over several rounds to establish areas of agreement.

The resulting definition describes dyslexia in terms of processing difficulties affecting the acquisition of reading and spelling.

It highlights reading fluency and spelling as important markers, recognises variation between individuals and acknowledges that several influences contribute to development.

It also recognises the frequent overlap between dyslexia and other developmental difficulties.

Why does reading fluency matter?

Reading accurately and reading fluently are related, but different.

Someone may work out words correctly while reading slowly or with considerable effort. This can make keeping up with written information difficult, even when they understand the subject well.

For example, a teenager might read a textbook accurately but need much longer than expected to finish the assigned section. An adult may manage a report well when given time but find reading under pressure considerably harder.

Simply asking whether someone can read does not capture the whole experience.

Why is spelling important too?

Spelling can remain difficult even when reading has improved.

A person might recognise a word when reading but struggle to produce its spelling independently. They may spend considerable time checking or choose a different word because they are unsure how to spell the one they intended.

Spelling deserves attention in its own right. It should not be overlooked because someone reads books, achieves good grades or communicates their ideas confidently.

Does everyone with dyslexia have the same difficulties?

No. The definition recognises that dyslexia varies between people and that difficulties occur along a continuum.

This does not mean that one label can neatly describe how manageable someone’s life will feel. The effect depends partly on the tasks they face, the support available and the approaches they have developed.

Two people with similar reading skills may experience very different demands at school or work.

That is why assessment and recommendations need to be individual.

What are phonological processing difficulties?

Phonological processing concerns how we work with speech sounds.

It includes recognising and manipulating sounds within words, remembering sound sequences and efficiently retrieving sound-based information.

These skills are relevant to learning to read and spell. However, phonological difficulties alone do not explain every person’s experience of dyslexia.

An explanation needs to consider how the different findings fit together.

What about working memory and orthographic skills?

The definition recognises that working memory, processing speed and orthographic skills can contribute to the impact of dyslexia.

Orthographic skills concern knowledge of written language, including letters, letter sequences and spelling patterns.

These areas can help explain an individual’s difficulties, but an assessor does not need to find difficulties in every one of them to identify dyslexia.

Difficulty with memory or processing speed alone does not establish a diagnosis.

Can dyslexia occur alongside other conditions?

Yes. Dyslexia can co-occur with developmental language disorder (DLD), ADHD, dyscalculia and developmental coordination disorder (DCD).

These are distinct conditions. A person may have one separately or experience more than one together.

For example, a child may need support with reading and spelling alongside help understanding spoken language. Another person may have literacy difficulties together with attention difficulties.

Recognising this overlap helps avoid attributing every problem to dyslexia. It can also indicate where another professional’s input would be useful.

What does this mean for a dyslexia assessment?

An assessment needs to consider the full pattern of evidence.

That includes developmental and educational history, current concerns, teaching and support, observations during assessment and test results.

The practical questions matter too. How much effort does reading take? What happens when the person encounters unfamiliar words? How do spelling difficulties affect their writing?

The definition provides a framework for understanding dyslexia. It does not turn assessment into a checklist or make one score decisive.

Does the definition mean that everyone needs reassessment?

An updated definition does not, on its own, mean that someone’s previous diagnosis is invalid or that they automatically need another assessment.

Whether further assessment would be useful depends on their circumstances, current questions and any requirements for the intended use of a report.

If you already have a report, start by considering whether it explains your current needs and provides useful recommendations.

What does it mean for support?

The definition does not automatically change school provision, exam arrangements or funding. These have their own processes and requirements.

Its practical value is in encouraging careful understanding of the person’s literacy difficulties and the factors contributing to them.

Support should address the needs identified. That might include structured literacy teaching, ways to access written material or approaches that reduce unnecessary demands during learning.

For children, appropriate support should begin when difficulties are recognised rather than waiting for a diagnosis.

Understanding the person behind the definition

A definition helps professionals describe dyslexia. It cannot capture everything about the person experiencing it.

Their confidence, interests, history and views matter too.

My priority is to help people make sense of their experiences and identify useful support, while protecting self-esteem. Reading and spelling difficulties should never become a judgement about someone’s effort or worth.

A good assessment reflects current understanding and looks at the whole picture rather than a single score. If you'd like to know how that works in practice, read about dyslexia testing in Truro, or get in touch with any questions.

You can also explore my free courses, videos and self-help guides for clear information about dyslexia and related topics.

Further reading

The SpLD Assessment Standards Committee (SASC) downloads page includes its briefing paper on the published Delphi study and definition. Its FAQs provide further clarification for assessment practice.