Dementia can be caused by a number of different conditions; it is a symptom of neurodegenerative diseases like Alzheimer's, frontotemporal dementia or corticobasal degeneration. The term "dementia" describes a progressive, degenerative decline in cognitive function that gradually destroys memory and the ability to learn, reason, make judgments, communicate and carry out daily activities. While it often includes memory loss, memory loss by itself does not mean that a person has dementia. Dementia affects 17–25 million people worldwide.
Dementia is not a specific disease; it is a collection of symptoms that can be caused by a number of disorders, including neurodegenerative disease. The term "dementia" describes a progressive decline in memory or other cognitive functions that interferes in the ability to perform your usual daily activities (driving, shopping, balancing a checkbook, working, communicating, etc.). The deterioration is more than might be expected from normal aging and is due to damage or disease.