Review with the class that suffixes are meaningful word parts that are attached to the end of a word. You might want to further explain that adding a suffix to a particular word often changes the part of speech of the original word.
Divide the class into two groups. Ask one group to flip through a textbook or novel that you are reading in class in order to find at least ten words that do not end with a suffix. Instruct the other group to change the word’s part of speech by adding on a suffix. Then have the two groups switch jobs. Be sure to clarify with students that not all words can have suffixes attached to them.