heir apparent
noun [ C usually singular ] uk/ˌeər əˈpær.ənt/ us/ˌer əˈper.ənt/
法定继承人;当然继承人
the person with the automatic right to legally receive all or most of the money, property, titles, etc. from another person when they die
The Prince of Wales is the heir apparent to the throne. 威尔士亲王是王位的法定继承人。
（职位的）确定接替者，确定接班者
a person who seems certain to take the place of someone in power when that person stops working