Dictionaries and encyclopedias are among the best sources to use to acquaint yourself with correct terminology, and also, to find a general introduction to the subject matter. In the dictionary category, I have provided you with one internet index (Google) and an additional source providing authoritative definitions of Dyslexia.
This Google Index provides its readers with several links to organizations and how they define "Dyslexia." Each link may provide a definition, an acronym or a definition provided by an organization. This index is an excellent tool for parents, teachers, and students who need a quick reference to words associated with this disorder.
Word IQ provides several definitions of "Dyslexia" from the University of Miami School of Medicine.