Dementia is not a specific disease. Instead, it describes a group of symptoms affecting intellectual and social abilities severely enough to interfere with daily functioning. It is caused by conditions or changes in the brain. Different types of dementia exist, depending on the cause it occurs with certain diseases like Alzheimer's disease. Dementia affects memory, thinking, language, judgment and behaviour. Memory loss generally occurs in dementia but that does not mean one has dementia.
Attribution: Straight Talk Foundation