Aphasia is a speech disorder acquired after language development has been completed due to brain damage. The cause of this brain damage can be a stroke, a cerebral hemorrhage, a traumatic brain injury or a brain tumor. Depending on the area of the brain damaged, different language skills can be affected. Difficulties can occur in understanding language, finding words, reading or writing, grammar or memory. The severity of the disorder can also vary. The more severe the damage to the areas of the brain that control language, the more extensive the aphasic symptoms will be. The patient's thinking and knowledge are not affected, but the aphasic person may have problems with concentration, memory, arithmetic or spatial orientation.

Communication can be severely impaired by aphasia. Those affected suffer from the loss of speech and are often desperate and depressed. It is also very difficult for relatives to communicate with the person affected and to cope with the new situation.