Aphasia is a condition that is acquired, generally because of some form of left hemisphere brain damage from a stroke or other damage to the head. A brain tumor, brain hemorrhage, Alzheimer's or Parkinson's diseases may also cause aphasia. Those afflicted with aphasia have a lot of trouble with their speech and language abilities. It is usually difficult to understand the speech of someone who has aphasia. Aphasia can affect the speech as well as the ability to understand any language, whether it is spoken or written. Partial language impairment is still considered to be aphasia. A person with aphasia may be able to write notes to make themselves understood, or they may still have some speech, but no writing ability at all. Some can sing and pronounce each word clearly, yet are unable to speak the lyrics at all. There are several types of aphasia, and those who suffer from them are generally eligible for Social Security Disability, for they are unable to participate in life, much less hold down a job.