Abstract Aphasias are language disorders related to brain disease. Most are related to lesions or disorders of the left hemisphere, since the great majority of right-handed people and over half of left-handed people have left hemisphere dominance for speech. Aphasias are often caused by strokes, though brain injuries, brain tumors, and other pathological disorders such as neurodegenerative diseases and dementia can produce language disorders. The major types of aphasia are Broca's, Wernicke's, global, conduction, anomic, and transcortical aphasias. In addition, syndromes of subcortical aphasia have been described. Alexias and agraphias, acquired disorders of reading and writing, are closely related to aphasia. Aphasia often improves over time, except for those cases resulting from neurodegenerative conditions. Speech and language therapies help to facilitate recovery. Newer, experimental treatments for aphasia are under investigation.