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'Dyslexia is a specific learning difficulty which primarily affects reading and writing skills. However, it does not only affect these skills. Dyslexia is actually about information processing. Dyslexic people may have difficulty processing and remembering information they see and hear, which can affect learning and the acquisition of literacy skills. Dyslexia can also impact on other areas such as organisational skills. It is important to remember that there are positives to thinking differently. Many dyslexic people show strengths in areas such as reasoning and in visual and creative fields.'
– British Dyslexia Association (2026)
The Delphi definition of dyslexia was agreed and officially published in February 2025, following three years of research and consultation with a wide range of experts. It replaces the Rose (2009) definition as the updated standard for identifying dyslexia in education and research settings. The new definition identifies similar underlying cognitive indicators of dyslexia as the previous Rose (2009) definition, and there is no need for a further assessment if diagnosed under this definition.
The Delphi Definition
Nature
The nature and developmental trajectory of dyslexia depends on multiple genetic and environmental influences.
Manifestation
Dyslexia is a set of processing difficulties that affect the acquisition of reading and spelling. The most commonly observed cognitive impairment in dyslexia is a difficulty in phonological processing (i.e. in phonological awareness, phonological processing speed or phonological memory). However, phonological difficulties do not fully explain the variability that is observed. Working memory, processing speed and orthographic skills can contribute to the impact of dyslexia.
Impact
In dyslexia, some or all aspects of literacy attainment are weak in relation to age, standard teaching and instruction, and level of other attainments. Across languages and age groups, difficulties in reading and spelling fluency are a key marker of dyslexia.
Variance and Co-occurrence
Dyslexic difficulties exist on a continuum and can be experienced to various degrees of severity. Dyslexia can affect the acquisition of other skills, such as mathematics, reading comprehension or learning another language. Dyslexia frequently co-occurs with one or more other developmental difficulties, including developmental language disorder, dyscalculia, ADHD, and developmental coordination disorder.
Holden, C., Kirby, P., Snowling, M.J., Thompson, P. A., Carroll (2025) Towards a Consensus for Dyslexia Practice: Findings of a Delphi Study on Assessment and Identification, Dyslexia, 31(1). https://doi.org/10.1002/dys.1800