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 and 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
National Institutes of Child Health and Human Development (2002)