Memory loss is the loss of memory, the faculty of the mind by which data or information is encoded, stored, and retrieved when needed. Memory loss is usually described as forgetfulness, absent-mindedness, or a physical or mental disorder such as amnesia. Memory loss can be partial or total, and it is normal when it comes with aging. Sudden memory loss is usually a result of brain trauma and it may be permanent or temporary. When it is caused by medical conditions such as Alzheimer's disease, the memory loss is gradual and tends to be permanent.