The Probert Encyclopaedia of General Information

HEIR-APPARENT

An heir-apparent is someone who 'are such whose right of inheritance is indeafsible provided they outlive the ancestor; as the eldest son, who must be heir to the father when ever he happens to die'. Blackstone. That is, someone whose right of inheritance cannot be superseded by the birth of another, unlike an heir-presumptive whose right of inheritance can be superseded by the birth of another.
Research Heir-Apparent