An heir is a person who inherits wealth, power, or a position following another person’s death or decision to give up power:
Prince William is an heir to Queen Elizabeth. When she dies, he will probably become the King of England.
When the old owner of the company died, one his heirs took over the management of the business.
Believing he would one day inherit a lot of money as an heir to a vast fortune , Tony quit college and moved to California to become a surfer.
An heir to the throne was not apparent. This lead to serious conflict within the family.
An heiress to a rich European manufacturer walked into the jewelry store and purchased merchandise worth hundreds of thousands of dollars. (When the an heir is female, we use the word "heiress; however; heir can be applied to both men and women.)
Note: The pronunciation of the word "heir" is the same as it is for the word "air." The "h" in "heir" is silent.