Terminal illnesses, also known as end-stage diseases, are diseases that cannot be cured or adequately treated and are expected to result in the death of the patient. This term is commonly used for progressive diseases such as cancer, dementia, or advanced heart disease. In popular use, it indicates a disease that will progress until death with near absolute certainty, regardless of treatment. Patients with terminal illnesses may be referred to as terminal patients, terminally ill, or simply as being terminal individuals. There is no standardized life expectancy for a patient to be considered terminal, although it is generally months or less. The life expectancy for terminal patients is a rough estimate given by the physician based on previous data and does not always reflect true longevity.