<P> Aphasia is an inability to comprehend and formulate language because of damage to specific brain regions . This damage is typically caused by a cerebral vascular accident ( stroke ) , or head trauma ; however , these are not the only possible causes . To be diagnosed with aphasia , a person 's speech or language must be significantly impaired in one ( or several ) of the four communication modalities following acquired brain injury or have significant decline over a short time period ( progressive aphasia ) . The four communication modalities are auditory comprehension , verbal expression , reading and writing , and functional communication . </P>
aphasia is a term defining difficulty or loss of ability to
comprehend and formulate language