There are many definitions of dyslexia. Among these are the following:

Dyslexia is best described as a combination of abilities and difficulties that affect the learning process in one or more of reading, spelling and writing. Accompanying weaknesses may be identified in areas of speed of processing, short term memory, sequencing and organisation, auditory and/or visual perception, spoken language and motor skills. It is particularly related to mastering and using written language, which may include alphabetic, numeric and musical notation.

British Dyslexia Association

Dyslexia is evident when accurate and fluent word reading and/or spelling develops very incompletely or with great difficulty.

British Psychological Society


Dyscalculia is a learning difficulty involving the most basic aspects of arithmetic skills. The difficulty lies in the reception, comprehension or production of quantitative and spatial information. Students with dyscalculia may have difficulty in understanding simple number concepts, lack an intuitive grasp of numbers and have problems learning number facts and procedures. These can relate to basic concepts such as telling the time, calculating prices and handling change.

Department of Education & Skills


A student with Dyspraxia/Development Coordination Disorder (DCD) may have an impairment or immaturity in the organisation of movement, often appearing clumsy. Gross motor skills (relating to balance and coordination) and fine motor skills (relating to manipulation of objects) are hard to learn and difficult to retain and generalise. Writing is particularly laborious and keyboard skills difficult to acquire. Individuals may have difficult in organising ideas and concepts. Pronunciation may also be affected and people with Dyspraxia/Development Coordination Disorder may be over/under sensitive to noise light and touch. They may have poor awareness of body position and misread social cues in addition to those shared characteristics common to many SpLDs.

British Dyslexia Association


Children with the disorder display inattentiveness and impulsiveness and those with the ADHD diagnosis, hyperactivity. There is a strong genetic basis but environmental causes including brain damage and food intolerances have also been associated with the disorder.

Department of Education & Skills


Autism is characterised by the ‘triad of impairments’ – impairments of non-verbal and verbal communication, social understanding and social behaviour and thinking and behaving flexibly according to the situation. Onset is before 30 months. 75-80% of children with a diagnosis of autism will also have moderate or severe learning difficulties. Many children also have ‘co-morbidities’, such as epilepsy or ADHD. A small proportion of children with autism have islets of, sometimes exceptional, ability in areas such as drawing, music and mathematics.

Department of Education & Skills


The term autistic spectrum disorder was suggested by Wing in 1996 to acknowledge that there are different subgroups, and that all individuals within these subgroups share the triad of impairments.

Department of Education & Skills


Asperger’s is similar to autism except that children with the syndrome have higher intellectual abilities and better language development than the majority of children with a diagnosis of autism. There is a theoretical debate over whether Asperger’s syndrome is the same as high-functioning autism. The main clinical features of Asperger’s syndrome are a lack of empathy and difficulties in understanding the reciprocal nature of conversations and relationships. Individuals can be pedantic with repetitive speech and develop an intense fascination for certain topics. Many also are clumsy and have coordination problems and difficulties in attending to more than one aspect of a task simultaneously. Diagnosis is usually later than for children with autism.

Department of Education & Skills


Sensory experiences include touch, movement, body awareness, sight, sound, and the pull of gravity. The process of the brain organising and interpreting this information is called sensory integration. Sensory integration provides a crucial foundation for later, more complex learning and behaviour.

For most children, sensory integration develops in the course of ordinary childhood activities. Motor planning ability is a natural outcome of the process, as is the ability to adapt to incoming sensations. But for some children, sensory integration does not develop as efficiently as it should. When the process is disordered, a number of problems in learning, development, or behaviour may become evident.

Sensory Integration International


This is a term originally coined by speech and language therapists for children who have difficulties in understanding the meaning of language and its social use, which affects their communication. These children also have difficulties with social interaction and imaginative play and have restricted interests. Like those with Asperger’s syndrome, children with semantic-pragmatic disorder will have average and above average intelligence. There is debate currently as to whether children with semantic-pragmatic disorder and children with Asperger’s syndrome are the same or different subgroups within the autistic spectrum.

Department of Education & Skills


This has been defined by the International Classification of Diseases (WHO, 1993) as:

  • Language skills, as assessed on standardised tests, are below the two standard deviations limit for the child’s age.
  • Language skills are at least one standard deviation below non-verbal IQ assessed on standardised tests.
  • There are no neurological, sensory or physical impairments that directly affect the use of spoken language, nor is there a pervasive developmental disorder.

A distinction is made between receptive language disorder, where comprehension is more than two standard deviations below age level and expressive language disorder, where only expressive language is severely affected, and where understanding and use of non-verbal communication and imaginative language functions are within the normal range.

The American Psychiatric Association’s Diagnostic and Statistical Manual (1994) definition is similar to the above and also includes mention that the language difficulties interfere with academic or occupational achievement or with social communication.

Specific language impairment (SLI) is not a homogenous disorder. It can affect the various subcomponents of language to varying degrees, resulting in each child presenting with a different profile of difficulty. The subcomponents affected can be receptive language.

  • Pragmatics
  • Expressive language Attention and listening
  • Word finding
  • Auditory memory
  • Speech/phonology

Royal College of Speech & Language Therapists


Child speech disorders may be developmental or acquired. Developmental speech disorders are distinguishable from speech delays by unusual patterns of speech development as evidenced in speech data analysis.

Royal College of Speech & Language Therapists