Dyslexia is a language-centered learning disability characterized by difficulty learning to read fluently and with accurate comprehension, difficulty spelling, and difficulty distinguishing between phonetic units despite having normal or above average intelligence and access to appropriate education. About 15-20 percent of the population exhibit some of the symptoms of dyslexia, and it occurs in people of all backgrounds and intellectual levels.

In addition, dyslexia is hereditary; dyslexic parents are very likely to have children who are dyslexic. While some dyslexics identify their disability when they are young, many people do not discover they are dyslexic until they get older.

Broadly speaking, dyslexia is a decoding issue wherein a reader has difficulty connecting a letter or a phoneme (a small group of letters that produce a particular sound) to the sound it makes. This leads to difficulty constructing words and sentences in speech and writing. As a direct results, dyslexics are often slower to speak, more prone to mispronunciation, and slower to gain a broad vocabulary. This is not a reflection of the intelligence of dyslexic learners; on contrary, people with dyslexia often have superior intelligence and creativity, curiosity, well-developed problem-solving skills and memories, and excellent ability to comprehend oral stories.

Dyslexia manifests a wide variety of symptoms. In popular culture, it is often depicted as involving a tendency to switch letters, reorder syllables, or engage in letter reversal or mirror writing, but these symptoms are actually relatively uncommon among dyslexics. Dyslexics can have issues that include speech and auditory problems (e.g. difficulty learning the alphabet; difficulty identifying syllables and rhyming words; difficulty distinguishing between similar sounds), spelling problems (e.g. leaving letters, especially vowels, out of words; switching the order of letters, especially if the changed order also produces a word: "tub" becomes "but" or "dose" becomes "does"), and reading problems (e.g. perceiving a word with added or subtracted letters; difficulty summarizing or memorizing written information; difficulty parsing the meaning of complex sentences).

There are a number of ways one can be tested for dyslexia. Often, a school or school district will choose to track a student’s reading ability with a screening test to determine if the student is reading at a particular level (usually equivalent to the 40th percentile nationally). Subsequently, the school may determine that the student needs intensive and personalized supplemental reading instruction before suggesting a diagnostic test. However, parents have the right to request a comprehensive evaluation under the Individuals with Disabilities Education Act (IDEA).