Qn- What is Dementia? Can we say that my mother is suffering from Alzheimer's disease?

Ans-Dementia is serious cognitive decline in a person.Alzheimers diease is
most common cause of dementia,
Alzheimer's disease is a specific form of dementia having very specific microscopic brain abnormalities.  However, in typical medical practice, we do not have the ability to see microscopic brain abnormalities.So it would be very difficult to say right at this moment, for this we must examine her and do some investigations.