A comma is used to separate a series of three of more things in a row. To help your child understand this concept, have them create a list. This list can be colors in a crayon box, foods they like to eat, etc. As they write a sentence that includes a list, have them go back and add commas. Remind them that there will be one less comma as there are words in their list. For example, the sentence might read “I like the colors green, blue, yellow, red and purple.” Five colors were listed in the sentence and four commas were used.