Mild cognitive impairment: Abbreviated MCI. A brain disorder in which thinking abilities are mildly impaired. Individuals with mild cognitive impairment are able to function in everyday activities but have difficulty with memory -- trouble remembering the names of people they met recently, remembering the flow of a conversation, and a tendency to misplace things. The individual may be aware of these difficulties and compensate with increased reliance on notes and calendars. The diagnosis of MCI relies on the fact that the individual is able to perform all their usual activities successfully, without more assistance from others than they previously needed. In this regard, MCI is different from dementia. In dementia, memory loss has progressed to such a point that normal independent function is impossible and the individual can no longer successfully manage their finances or provide for their own basic needs. Most (but not all) patients with MCI develop a progressive decline in their thinking abilities over time, and Alzheimer's disease is usually the underlying cause.