Cognitive disorder marked by an impaired ability to comprehend or express language in its written or spoken form; caused by diseases which affect the language areas of the dominant hemisphere; general categories include receptive, expressive, and mixed forms of aphasia.

Aphasia, also known as dysphasia, is an impairment in a person’s ability to comprehend or formulate language because of damage to specific brain regions. The major causes are stroke and head trauma; prevalence is hard to determine, but aphasia due to stroke is estimated to be 0.1–0.4% in developed countries...