Here are some examples:
* Teacher: One who teaches.
* Singer: One who sings.
* Writer: One who writes.
* Baker: One who bakes.
* Player: One who plays.
There are other suffixes that can also indicate "one who," but they are less common than "-er." These include:
* -ist: Often used for people who follow a particular ideology, profession, or art form. (e.g., artist, scientist, violinist)
* -ant: Often used for people who perform a specific action or function. (e.g., accountant, applicant, assistant)
* -or: Less common than "-er," but still used in some words. (e.g., actor, conductor, inventor)