In English you can use series commas when you list items. Separating items in a list helps clarify things. Imagine that you text a shopping list to your roommate Charlie, who’s at the store shopping for your birthday party. Everything’s on one line.
flashlight batteries butter cookies ice cream cake
How many things does Charlie have to buy? Perhaps only three:
flashlight batteries
butter cookies
ice cream cake
Or five:
flashlight
batteries
butter cookies
ice cream
cake
How does Charlie know? He doesn’t, unless you use commas. Here’s what Charlie actually needs to buy — all four items:
flashlight batteries, butter cookies, ice cream, cake
To put it in a sentence:
Charlie has to buy flashlight batteries, butter cookies, ice cream, and cake.
The commas between these items are signals. When you read the list aloud, the commas emerge as breaths:
Charlie has to buy flashlight batteries [breath] butter cookies [breath] ice cream [breath] and cake.
You need commas between each item on the list, with one important exception. The comma in front of the word and is optional. Why? Because when you say and, you’ve already separated the last two items. But if you want to throw an extra comma there, you’re welcome to do so. It’s your choice.
Never put a comma in front of the first item on the list.
Wrong: Charlie has to buy, flashlight batteries, butter cookies, ice cream and cake.
Right: Charlie has to buy flashlight batteries, butter cookies, ice cream and cake.
Also right: Charlie has to buy flashlight batteries, butter cookies, ice cream, and cake.
Also right, but not a good idea: Charlie has to buy flashlight batteries and butter cookies and ice cream and cake.
You don’t need commas at all in the last sentence because the word and does the job. Grammatically, that sentence is fine. In reality, if you write a sentence with three ands, your reader will think you sound like a little kid or a tape on continuous rewind.
Here’s a pop quiz. Punctuate the following sentence.
Belle requested a jelly doughnut a silk dress four sports cars and a racehorse in exchange for the rights to the computer code she had written.
Answer: Belle requested a jelly doughnut, a silk dress, four sports cars, and a racehorse in exchange for the rights to the computer code she had written. Note: You may omit the comma before the and.