The following is the current, updated version following the SASC presentation on the new definition of dyslexia on 15th May 2024:

• Dyslexia is primarily a set of processing difficulties that affect the acquisition of reading and spelling.
• 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.
• The nature and developmental trajectory of dyslexia depends on multiple genetic and environmental influences.
•  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.
• 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, orthographic skills and processing speed problems can contribute to the impact of dyslexia and therefore should be assessed.
• Dyslexia frequently co-occurs with one or more other developmental difficulty, including developmental language disorder, dyscalculia, ADHD, and developmental coordination disorder.

For more information about the Delphi study, through which the definition was developed, can be downloaded from the SASC website: https://www.sasc.org.uk/