The words painter, teacher, starter, and thinker all end with the suffix er. What does the suffix -er mean?

The suffix -er typically indicates a person or thing that performs a certain action or has a certain characteristic. In the examples given, the suffix -er is used to identify a person who carries out the action of painting, teaching, starting, or thinking.

The suffix -er is known as a derivational suffix and is commonly used in English to form nouns and, less commonly, adjectives. In this case, the suffix -er is added to the end of a base word to create a noun that denotes a person or thing that performs or is associated with the action or quality described by the base word.

For example:
- Painter: A painter is someone who paints.
- Teacher: A teacher is someone who teaches.
- Starter: A starter is something or someone that starts or initiates something.
- Thinker: A thinker is someone who thinks deeply or engages in intellectual activities.

So, in general, the suffix -er changes a verb into a noun indicating a person or thing that performs the action of the verb.