abrupt or recent onset
generally progressive and irreversible in nature as less than 5% of dementias are reversible 
generally reversible in nature as approximately 90% of delirium cases are reversible 
non-fluctuating with a normal level of consciousness
effects one’s ability to function independently
hallucinations and delusions may be present
is not a normal part of the aging process
patients with an underlying history of dementia are more susceptible to developing delirium
For more comparisons between dementia and delirium, follow this link.
Don't forget - memory loss in isolation does not always mean dementia!