Aphasia is a term used to describe the loss of language or the ability to communicate, typically due to brain damage. Mutism is a speech disorder characterized by the inability to speak. Lack of speech development in children can occur due to deafness or hearing problems. In people who have developed speech, the onset of inability to speak can signal a stroke or other type of brain damage. Head injury, dementia, and brain tumors may be associated with the loss of speech or language functions.