Immortality is the supernatural ability of eternal youth and immunity to any natural ailment of the body, mind, or soul as well as the ability to live forever and never die. Immortals can still be killed, though it has to be by certain means.
Vampires are immortal, and as such, they stop aging the moment they become a vampire. This can mean some, such as Anastasia, remain as children for hundreds of years, despite their mind progressing.
Witches can also make themselves immortal through spells. Stephanie used to be immortal until Ethan , Benny , and Sarah ruined her immortality spell. Now reduced to her true age, she works as a lunch lady.