With that said, I’m going to limit this post to a discussion of only one use — the comma with “and.” Even that can be a little confusing because the conjunction “and” can be used to connect everything from items in a grocery list to events in a child’s day.
Let’s get down to specifics. When “and” is used to connect two complete sentences, there is usually a comma before the “and” (never after). Example: The students had to work together on the project in groups of three, and each group had to decide what part of the project to work on.
However — and here comes an exception — when the sentences are short, the comma is often optional. Example: The freshmen are scheduled for orientation on Monday and the sophomores are scheduled for Tuesday. Didn’t I warn you that commas are confusing?
Style books even disagree as to when a comma is optional or not. Take the case of what is referred to as the Oxford comma. That’s a fancy name for the comma used before the “and” in a list. Example: The scientists collected the specimens, cataloged them, and planned their research. The comma after “them” is the Oxford comma. A grammar book from the 1980s described the use of this comma as “old-fashioned.”
Other grammarians have been quick to point out, however, cases in which omitting that final comma in a series sometimes leads to misunderstandings. Here is a humorous example: The young reporter interviewed the senator’s rivals, a prostitute and a bank robber. No problem getting elected with rivals like that! But not all examples are humorous. In this sentence, using or omitting that Oxford comma may make a difference in what kind of treatment a patient receives: The patient needs to be scheduled for physical therapy, massage and whirlpool. Is the patient to receive three different therapies or only two? Since there is a possibility of misunderstanding, I would suggest always using that last comma in a series, just to be safe.
Finally, there is one place you should never use a comma, and that is when the “and” is connecting only two items. Example: That senator supported reproductive rights and gay marriage. The two items can also be longer. Example: My dog ran away one night and didn’t return for a week. If there are only two items and there is not a complete thought on either side of the “and,” then a comma is not needed.
Hopefully, this little discussion helps boost your confidence in using a comma with “and” — or not. If you still have questions, feel free to comment. And stay tuned for more posts about that crazy squiggle called a comma!