The suffix "ER" typically indicates a person who performs a certain action or is associated with a particular role. In the examples you provided:
- "Teacher" refers to someone who teaches.
- "Preacher" refers to someone who preaches.
- "Answerer" (though not explicitly mentioned, it follows the same pattern) would refer to someone who answers.
In these cases, "ER" denotes the person who performs the action of the verb.