Dyslexia is one of several distinct learning disabilities.

It is characterised by a difficulty with reading and writing that often appears to be surprising in a child who otherwise appears capable and academically promising.

Most current definitions of dyslexia focus on the fact that "accurate and fluent word reading and/or spelling develops very incompletely or with great difficulty". This focuses on literacy at the 'word level' and implies that the problem is severe and persistent despite appropriate learning opportunities (The British Psychological Society 1999). Spelling, comprehension, reading accuracy, reading rate, word identification and phonological coding are all affected.

It is now well recognised that dyslexia is commonly associated with difficulties with phonological awareness and processing. In simple terms, this refers to the ability to hear and manipulate the separate sounds within words (phonemes). Although such difficulties can be detected orally at an early age, they are frequently overlooked and the problem becomes most apparent when the child struggles to learn to read in the early years of schooling. In the reading process, lack of phonological awareness skills leads to difficulty recognising that sounds can be represented by letters or groups of letters within written words (often called Phonics at school).

It is also now accepted that there is a strong hereditary component in dyslexia - that is, it runs in families. It used to be thought that it affected far more boys than girls, but recent research tends to show that it is more evenly distributed. It appears to be that it is more noticeable in boys in the classroom situation.