The current definition from the International Dyslexia Association states:

“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 knowledge.”