A predecessor is a person who had a certain position before the current individual. For instance, you would say that Barack Obama’s predecessor is George W. Bush. The predecessor of Aaron Rodgers is Brett Favre. “Predecessor” could also be used to refer to things in general and not just people. The predecessor to the Nintendo Wii is the Nintendo GameCube.
It is important to note that a “predecessor” is the person (or thing) that immediately preceded the current one. Richard Nixon is not the predecessor to Bill Clinton in the context of saying they were both United States Presidents. It is also important to note that other words may be more appropriate for other circumstances. For instance, the precursor to AIDS is HIV. Other related terms include ancestor and forefather, neither of which have exactly the same meaning as predecessor.
A successor, on the other hand, refers to a relationship that goes in completely the opposite direction. While George W. Bush is the predecessor to Barack Obama, Barack Obama is the successor to George W. Bush in regards to the Presidency of the United States. As before, “successor” is oftentimes used in the context of people in positions, jobs, offices, or titles, but it can also be used for things. The successor to the Nexus S smartphone is the Galaxy Nexus.
In the context of familial relationships, particularly when it comes to royalty, “heir” is another term that has a similar meaning to “successor.” The heir to the throne will be the successor to the throne. He (or she) is the next person in line for that position and will inherit it.
Just as it is very easy to get poisonous and venomous mixed up, predecessor and successor can be mixed up too. Hopefully this post has help to clarify the difference. Do you have a suggestion for a future Grammar 101 post? Let me know through the comment section below.