Definition - What does Heir mean?
An heir is a person who is legally entitled to assume the position, or to aquire the property, of a person after his or her death. The term heir typically refers to a male; while the term heiress refers to females with entitlements of inheritance. Sometimes people choose their heirs before they die, and sometimes heirs are simply chosen by being the next of kin to the decedent.
Justipedia explains Heir
An example of a position for which an heir may be named is king of a kingdom. For example, the throne of England has been passing from heir to heir for thousands of years. Estates and other forms of property can also pass to heirs. For example, a man may choose his son as his heir, and pass along his estate to him after he dies. Heirs can also inherit controlling interests in businesses through stock options, or other means.