Aphasia refers to a language difficulty. Aphasia can impact all four areas of language: listening, speaking, reading, and writing. The severity and combination of difficulties varies from person to person, so each individual's experience with aphasia is unique. It can result from damage to the structures of the brain that control language. Possible causes include stroke, traumatic brain injury (TBI), brain infection, brain tumor, or degenerative diseases. Common signs include reduced understanding of speech, especially longer sentences, difficulty reading, trouble naming familiar people or objects, using made-up words, substituting incorrect words, getting stuck on certain words or phrases, difficulty forming complete sentences, and problems with writing.