Dyslexia is a specific learning disability that is neurobiological 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 classroom instruction. Secondary consequences may include problems in reading comprehension and reduced reading experience that impede growth of vocabulary and background knowledge.
-Definition of Dyslexia Adopted by the IDA Board of Directors