You don't have to go by this definition exactly, it's just the basic idea of a witch. If you have anything you want to add to this--our--working definition of a witch, please post it in this topic.
A witch is simply a human being who is able to harness and control magic. They are not immortal. In fact the only abnormal thing about witches is their magic.
A witch is not necessarily a woman, but also refers to a man who uses magic. However the term has come to be understood as more of a female human only, nowadays.
Witches are born with their magic but sometimes it is possible for a regular human to learn to use magic, as well.
Another term for a witch would be a spell-caster.
Definition According To Webster:
Witch:
n. 1: one that is credited with usually malignant supernatural powers ; especially : a woman practicing usually black witchcraft often with the aid of a devil or familiar : sorceress — compare warlock 2: an ugly old woman : hag 3: a charming or alluring girl or woman 4: a practitioner of Wicca
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