Dementia is the general term for a group of symptoms that affect memory, thinking, language, and daily function. Alzheimer’s disease is the most common cause of dementia. So the two terms are related, but they do not mean the same thing. Dementia describes what is happening, while Alzheimer’s describes one of the diseases that can cause it. In simple terms, all Alzheimer’s is dementia, but not all dementia is Alzheimer’s. The NHS also notes that Alzheimer’s and vascular dementia together make up most cases. If someone has symptoms, a doctor needs to assess the cause.