The only solidly defining element is blood drinking. So anyone that drinks blood to survive is a vampire.

Ok. A vampire is dark and mysterious. Blood and fangs. They feel cold, but look hot. I am the Twilight freak, so I know this stuff. Check out my forum, "I Am Vampire " for more answers to what a vampire is. P.S.- Post a comment for "I Am Vampire."

i was born a vampire!!! yet i hardly drink blood (ill be killed if i did) so basically,vampires dont actully have many powers!!!

Vampire becomes everyone who has been biten by another vampire and has been intentionally changed by it (vampires choose if they just want blood or if they want to convert a human into a vampire).After that the bitten people are immortal and they need to find blood to survive otherwise they suffer and eventully die.And of course they have the super powers you know.
I hope I helped.