What is Dyslexia?
The most widely accepted current definition of dyslexia is the following:
Dyslexia is a specific learning disability that is neurological in origin. It is characterized by difficulties with accurate and / or fluent word recognition and by poor spelling and decoding abilities. These difficulties typically result from a deficit in the phonological component of language that is often unexpected in relation to other cognitive abilities. These difficulties persist even with the provision of effective classroom instruction. Secondary consequences may include problems in reading comprehension and reduced reading experience that can impede growth of vocabulary and background knowledge.
This definition was also adopted by the Board of the International Dyslexia Association in 2002.
From Dyslexia: A Brief for Educators, Parents, and Legislators in Florida by Joseph K. Torgesen, Barbara R. Foorman, Richard K. Wagner
What is Severe Dyslexia?
It is hard for some children to learn how to read. But for a few it is even harder than for most. About 3 to 5% of all children have severe reading disabilities that do not respond substantially even with the best help. These children can do a lot of things but they struggle learning how to read. Often they have other family members who had learning problems.
The Dyslexia Research Registry has been established to link families who have a child with severe dyslexia with researchers who study dyslexia.