Dementia:

The medical term for a group of symptoms that describes a loss of intellectual ability, including loss of mental processes (e.g., vocabulary, abstract thinking, judgment, memory loss, physical coordination) that interfere with daily activities. The symptoms can be brought on by degenerative diseases (e.g., Alzheimer's, Huntington's and Parkinson's diseases), vascular diseases or stroke, metabolic disorders (thyroid, liver kidney dysfunction or certain vitamin deficiencies), AIDS, drugs and alcohol, or psychiatric disorders. Some dementing disorders may respond to treatments, others do not.