Dementia can be defined as an acquired syndrome of decline in memory and other cognitive functions. Dementia affects a patient's daily activities, although the patient retains their normal level of attention and consciousness. Therefore, delirium is not categorized as a dementia since it involves a loss of alertness. Characteristic changes of dementia can be categorized into three areas, cognitive (memory, language, visuospatial abilities), functional (activities of daily living and instrumental activities of daily living), and behavioral (personality changes, agitation, depression, psychosis). These dementia characteristics represent a decline from a patient's previous level of function.