# 3 Dyslexia defined

There are two types of dyslexia: acquired dyslexia and developmental dyslexia. Acquired dyslexia, called ‘alexia’, is caused by trauma or brain pathologies like stroke, resulting in partial or complete reading inability. Developmental dyslexia, often hereditary and present at birth, is typically what people refer to today.

The definition of dyslexia has evolved since the 1880s and remains a debated topic, unlike other neurodivergent conditions like Attention Deficit Hyperactivity Disorder (ADHD), which has universally accepted definitions and clear diagnostic criteria. Various stakeholders, including researchers, advocates, practitioners, and legislators, have contributed to the evolution of dyslexia definitions, each capturing different aspects of the condition. This ongoing dialogue enhances our understanding of this complex condition over time. By looking into all of this, you’ll see how our understanding of dyslexia has changed over the years. But more than that – you’ll have a fuller picture of what dyslexia really is. It’s a complex condition, but the more you know about it, the better you can understand it.

OpenLearn - Understanding dyslexia
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