successor

noun

1. A person or thing that immediately follows another in holding an office or title.

   “George W. Bush was successor to Bill Clinton as President of the US.”

   “After Li Tan's death in 1625, Hsu Hsin-su (許心素), leader of the Chang-chou people dwelling in and around the city of Hsia-men (廈門, or Amoy), emerged as his successor.”

   “As Di Matteo celebrated and captain John Terry raised the trophy for the fourth time, the Italian increased his claims to become the permanent successor to Andre Villas-Boas by landing a trophy.”

2. The next heir in order or succession.
3. A person who inherits a title or office.
4. The integer, ordinal number or cardinal number immediately following another.

   “A limit ordinal is not the successor of any ordinal.”