Hi, I'm Heather Kamins for About.com, and I'm here to talk to you about how to use a comma.The basic function of the comma is to guide readers through a sentence. So although there are a lot of specific rules to using commas, that's really the principle one you want to keep in mind. One of the more common uses for commas is to separate items in a list.So for example: She's in the office Monday, Wednesday, and Friday. You put commas in between those three items in the list, Monday, Wednesday, and Friday.You can also use a comma with a conjunction, such as and or but, to turn two complete sentences into one complete sentence.So for example: He grew up in Georgia, but now he lives on the West Coast.Commas are also used to set off introductory phrases. For example: While she ate, her sister finished cooking. You put a comma after ate. That's also a good example of how commas can help prevent confusion in a sentence. If you didn't have that comma, it would read: While she ate her sister finished cooking.You'll often find commas within the pauses in a sentence, but not always, and it's important to learn the specific rules for using commas, because grammar checkers won't always catch those errors.Thanks for watching. To learn more, visit us on the web at About.com.