Dyslexia is a learning difficulty that primarily affects the skills involved in accurate and fluent word reading and spelling.
Characteristic features of dyslexia are difficulties in phonological awareness, verbal memory and verbal processing speed.
Dyslexia occurs across the range of intellectual abilities.
It is best thought of as a continuum, not a distinct category, and there are no clear cut-off points.
Co-occurring difficulties may be seen in aspects of language, motor co-ordination, mental calculation, concentration and personal organisation, but these are not, by themselves, markers of dyslexia.
A good indication of the severity and persistence of dyslexic difficulties can be gained by examining how the individual responds or has responded to well founded intervention.
This definition appears on page 10 of the independent report by Sir Jim Rose to the Secretary of State for Children, Schools and Families June 2009: Identifying and Teaching Children and Young People with Dyslexia and Literacy Difficulties