dyslexia
n. a neurologically based learning disability manifested as severe difficulties in reading, spelling, and writing words and sometimes in arithmetic. Dyslexia is characterized by impairment in the ability to process sounds, that is, to make connections between written letters and their sounds; written work is often characterized by reversal errors. It can be either acquired (in which case it is often referred to as alexia) or developmental (see developmental dyslexia), is independent of intellectual ability, and is unrelated to disorders of speech and vision that may also be present. It is not the result of lack of motivation, sensory impairment, inadequate instructional or environmental opportunities, emotional disturbances, or other such factors. Since the 1960s, information-processing and other psychological accounts of acquired dyslexia have prompted investigators to subdivide it into two general classes: (a) visual word-form dyslexia, which is characterized by difficulty in the visual analysis of written words; and (b) central dyslexia, which is characterized by difficulty in later stages of the reading process (i.e., pronunciation and comprehension). Various types and subtypes of dyslexia, both acquired and developmental, have also been proposed, but there is no universally accepted system of classification. See also reading disability; reading disorder. —dyslexic
adj.