Aphasia is a disorder caused by damage to the parts of the brain that control language. It can make it hard for you to read, write, and say what you mean to say. It is most common in adults who have had a stroke. Brain tumors, infections, injuries, and dementia can also cause it. The type of problem you have and how bad it is depends on which part of your brain is damaged and how much damage there is.
There are four main types:
Some people recover from aphasia without treatment. Most, however, need language therapy as soon as possible.
NIH: National Institute of Neurological Disorders and Stroke