What is the difference between Alzheimer's and dementia?

Here is for starters.
http://www.alz.org/dementia/types-of-dementia.asp

Hi soulful good question....so many times we hear the term dementia when we should hear the term 'a dementia'. Glad is spot on there are loads of different types of dementia - which I imagine one day will be given different names as we realise they perhaps evolve from entirely different sources (thats possible but I know nothing in this arena of research)

You can only assess most dementias - for example vascular dementia can be actually seen to be affecting the individual via CT scans ...yes? Well no.... it is just an indicator. Its a bit like if it looks like a duck walks like a duck then chances are its a duck unless of course it honks like a goose in which case you might need to rethink your assessment

The same goes for the various dementias. Many appear similar in the early stages but change later and only through careful continuous monitoring can a professional say YES this is dementia and it it this type of dementia ....maybe

I know that's not a satisfactory answer but in truth there isn't one. Very often Dementias are labelled Alzheimers but as the disease progresses there can be an adjustment to that assessment. My mum was diagnose with Alzheimers then Mixed dementia when she showed signs of Vascular dementia but now they are not so sure if it is that or something else. And thats after 5 years so just see it as the blind leading the blind for no-one quite knows YET

Alzheimers and many other dementias cannot be diagnosed except postmortem by autopsy. Doctors make their best guess on many types of dementia based on symptoms.

There are more than 70 types of dementia, Alzheimer's is one of them and is the most common in about 70% of cases.