(redirected from dyslectics)
Also found in: Dictionary, Thesaurus, Encyclopedia.




The word dyslexia is derived from the Greek word, dys, meaning poor or inadequate, and the word lexis, meaning words or language. Dyslexia is a learning disorder characterized by problems in processing words into meaningful information. This is most strongly reflected in difficulty in learning to read.


For almost a century after dyslexia was first described in a British medical journal in 1896, it was thought to be the result of a visual processing problem. Various forms of eye training were tried to improve visual perception; these generally failed. Today, researchers understand that dyslexia is a problem that arises from difficulties or inefficiencies in the brain in analyzing and processing individual letter sounds (called phonemes) and blending them into words at a speed that allows comprehension and fluency. Thus, the most prominent sign of dyslexia is difficulty in learning to read. Nevertheless, people with dyslexia may have other language-related deficits such as problems understanding rapid speech, difficulty in following complex or multi-part instructions, or trouble remembering things in correct sequence. Because of the difficulty in processing letter sounds, people with dyslexia are often poor spellers. It was once thought that letter reversal (e.g., from instead of form) was a sign of dyslexia, but as of 2008, research finds that although dyslectics do reverse letters, this problem is no more common in people with dyslexia than in those without the disorder.
Reading disorders are the most common typo of learning disorder, and dyslexia is the most common reading disorder. Between 15% and 20% of American elementary school children have significant, continuing difficulties with learning to read, reading fluency, and/or reading comprehension, but only about 5% are referred for special help in reading. Of those, between 65% and 75% are boys. Dyslexia occurs in people of all races, and income levels, however, African-American children with dyslexia are more likely to be misdiagnosed and mislabeled as mildly mentally retarded. Dyslexia is not linked to low intelligence (low IQ). Many people with the disorder have average or above average intelligence and show an unexpected difference between achievement and aptitude, although this is not a requirement for a diagnosis of dyslexia. The disorder is not something that is outgrown; most children with dyslexia continue to read more poorly than their peers in adulthood despite learning various strategies to minimize the disorder.

Causes and symptoms

The underlying cause of dyslexia is not known, although research suggests the condition is often inherited. Using positron emission tomography (PET) scans and functional magnetic resonance imaging (fMRI), researchers have been able to track the parts of the brain that become active when people with and without dyslexia read. Their general conclusion is that the brains of people with dyslexia are organized differently than those without the disorder and that this different organization results in less concentrated and efficient analysis and processing of the written representation of letter sounds into meaningful information.
Common signs of dyslexia include problems with:
  • identifying single letters or words

  • breaking down words into their individual sounds(phonemes)

  • blending individual sounds into meaningful words at an appropriate speed

  • reading comprehension

  • chronically reading below grade level

  • accurate spelling

  • transposing letters in words

  • following complex directions

  • confusion with opposites (up/down, early/late, and so on)


Anyone who is suspected to have dyslexia should have a comprehensive evaluation, including hearing, vision, and intelligence testing. The test should include all areas of learning and learning processes, not just reading. A trained reading specialist, school psychologist, private child neuropsychologist, or educational specialist may do the evaluation. In the United States, public schools are required to provide free and appropriate evaluations of children suspected of having a disability, usually within 60 days of a parent's or guardian's request. However, a parent or guardian must initiate the request in writing.
Diagnosis can be complicated by the presence of other disorders that affect learning. People with dyslexia often have attention deficit hyperactivity disorder (ADHD). There is such a strong correlation between ADHD and dyslexia that some experts recommend automatically evaluating any child who has a diagnosis of ADHD for a reading disorder. Other learning disorders such as difficulty putting thoughts into written form (dysgraphia), difficulty comprehending mathematics (dyscalculia), and auditory processing deficits also occur in children with dyslexia and may need to be tested for at the time of diagnosis in order to prevent mislabeling the child as mildly mentally retarded.


If a child is diagnosed with dyslexia, public schools are required to provide appropriate free education to address the disability. This often takes the form of an individual education plan (IEP) that incorporates some time each day spent with a reading specialist. Children appear to do best in programs that emphasize phonics- breaking words into sounds, then combining the sounds into words. If the school does not use a phonics-based program, parents may wish to supplement school-based instruction with a private program such as Orton-Gillingham or Lindamood-Bell that emphasizes letter-sound awareness. A multisensory approach combining sight, sound, and touch, is helpful to some children.


How well a person with dyslexia functions in life depends on the degree of disability, the presence of other learning disabilities, and the success of intervention strategies. Many successful and even famous people have dyslexia. Often they have succeeded by selecting careers that emphasized their many other strengths and abilities. Prognosis often is good if the dyslexia is diagnosed early, if the child has a strong self image with supportive family, friends, and teachers, and is actively involved in a good, individualized remedial program.

For Your Information



  • Hultquist, Alan M. What is Dyslexia?: A Book Explaining Dyslexia for Kids and Adults to Use Together. Philadelphia: Jessica Kingsley Publishers, 2008.

  • Nicolson, Roderick I. and Angela J. Fawcett. Dyslexia, Learning, and the Brain, Cambridge, MA: MIT Press, 2008.


  • "Dyslexia." MayoClinic.com. August 27, 2007 [cited February 19, 2009]. http://www.mayoclinic.com/health/dyslexia/DS00224.

  • "Learning Disorders." MedlinePlus. January 27, 2009 [cited February 19, 2009]. http://www.nlm.nih.gov/medlineplus/learningdisorders.html.


  • National Center for Learning Disabilities. 381 Park Avenue South Suite 1401, New York, NY 10016. Telephone: (212) 545-7510 or (800) 575-7373. Fax: (212) 545-9665. http://www.ncld.org.

  • Learning Disabilities Association of America. 4156 Library Road, Pittsburgh, PA 15234-1349. Telephone: (412) 341-1515. Fax: (412) 344-0224. http://www.ldaamerica.us.

Gale Encyclopedia of Medicine. Copyright 2008 The Gale Group, Inc. All rights reserved.


inability to read, spell, and write words, despite the ability to see and recognize letters; a familial disorder with autosomal dominant inheritance that occurs more frequently in males. adj., adj dyslex´ic.
Miller-Keane Encyclopedia and Dictionary of Medicine, Nursing, and Allied Health, Seventh Edition. © 2003 by Saunders, an imprint of Elsevier, Inc. All rights reserved.


Impaired reading ability with a competence level below that expected on the basis of the person's level of intelligence, and in the presence of normal vision, letter recognition, and recognition of the meaning of pictures and objects.
[dys- + G. lexis, word, phrase]
Farlex Partner Medical Dictionary © Farlex 2012


A learning disability marked by impairment of the ability to recognize and comprehend written words.
The American Heritage® Medical Dictionary Copyright © 2007, 2004 by Houghton Mifflin Company. Published by Houghton Mifflin Company. All rights reserved.


Pediatrics An inability or unexpected difficulty in learning to read despite adequate IQ, motivation and education Clinical Word-blindness, tendency to reverse letters and words Diagnosis Texas Primary Reading Inventory, functional MRI. See Congenital word blindness, Developmental reading disorder, Learning disability, Primary reading disability, Specific reading disability, Texas Primary Reading Inventory, Word blindness. Cf Reading retardation.
McGraw-Hill Concise Dictionary of Modern Medicine. © 2002 by The McGraw-Hill Companies, Inc.


Impaired reading ability with a competence level below that expected on the basis of the person's level of intelligence, and in the presence of normal vision, letter recognition, and normal recognition of the meaning of pictures and objects.
[dys- + G. lexis, word, phrase]
Medical Dictionary for the Health Professions and Nursing © Farlex 2012


Abnormal difficulty in reading or in comprehension of what is read, in a person of normal intelligence and emotional stability and who has had normal educational and cultural opportunities. The condition is familial and heritable and there is evidence of differences in areas of the brain that are also affected in acquired alexia. The basic difficulty appears to be in processing the sounds of speech and in the awareness that words can be broken down into smaller units of sound. Many dyslexic children respond well to remedial help especially if provided early.
Collins Dictionary of Medicine © Robert M. Youngson 2004, 2005



word blindness

impairment of the ability to read, write and speak, due to a brain disorder. Dyslexia is characterized by a discrepancy between high ability in some areas and poor performance in others. There are often sequencing difficulties which affect short-term memory so that multi-syllabic words cannot always be repeated or recalled.
Collins Dictionary of Biology, 3rd ed. © W. G. Hale, V. A. Saunders, J. P. Margham 2005


A condition characterized by difficulty with reading and spelling. Words may be read but not recognized or understood. It is independent of intelligence, motivation or visual correction. Its origin may be due to a disorder of the fast processing magnocellular visual system. The condition is commonly associated with the Meares-Irlen syndrome. See alexia; Meares-Irlen syndrome; developmental and perceptual screening test.
Millodot: Dictionary of Optometry and Visual Science, 7th edition. © 2009 Butterworth-Heinemann


Impaired reading ability with a competence level below that expected on the basis of the person's level of intelligence, and in the presence of normal vision, letter recognition, and recognition of the meaning of pictures and objects.
[dys- + G. lexis, word, phrase]
Medical Dictionary for the Dental Professions © Farlex 2012