heir:
a person who inherits, or is entitled by law or by the terms of a will to inherit, the estate of another; a person who inherits, or has been designated to inherit, a hereditary title or office.
heir apparent:
a person whose right of inheritance is established by law, provided he or she outlives the ancestor. See also primogeniture.
holographic will:
a will that is written entirely handwritten by the person whose signature it bears. Also known as an olographic will.