"When NOT to Use Commas": Oregon State Guide to Grammar

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When Not to Use Commas - Transcript
Written by J.T. Bushnell, Oregon State University Senior Instructor of English
Performed by Rachael Higham
Our last video showed you when to use commas, but it’s also important to know when not to use them. The simplest answer is, you probably don’t need any commas outside of the situations we’ve already described. They’re unnecessary, and throwing them into a sentence might cause readers to stumble, like throwing a branch into the trail where nobody’s expecting it. Let’s look closer at some places that don’t need commas.
As we discussed in the last video, you use commas to separate items in a list, but there are a few situations when we leave them out. The first is when we use conjunctions in their place: rock and tree and potato. No commas needed. The “ands” do their work. The second is when we list items vertically, or in bullet points:
  • rock
  • tree
  • potato
No commas needed. The page breaks do their work. And the last is when leave out the Oxford comma, which is the final serial comma, the one after “tree” in rock, tree and potato. We’ll discuss why in the next video.
There are also situations when you don’t need commas for parentheticals. Commas are actually one of three ways that we can separate parenthetical information from the rest of the sentence. The other two, parentheses and dashes, can take the place of the commas. We use parentheses to signal that the information is less important than the main sentence. We use dashes for more emphasis, more importance. We use commas for neutral emphasis, or equal importance.
When a parenthetical occurs at the end of a sentence, however, we don’t need the second comma. The first comma acts like the opening parenthesis, and the period takes the place of the closing parenthesis. We would never put a second comma right next to a period. It’s not necessary, and it just looks weird.
As for clauses, you might remember that you need a comma only when you shove something into the sentence before an independent clause. If you shove it in after an independent clause, on the other hand, you probably won’t need one. That’s true for phrases: from a distance, comma, this rock looks like a head; but, this rock looks like a head from a distance. No comma when the independent clause comes first. And it’s true for dependent clauses: when it gets startled, comma, the tree jumps into the canopy; but, the tree jumps into the canopy when it gets startled. No comma when the independent clause comes first.
Nor do you ever need a comma inside an independent clause. Not between the subject and predicatethe tree swallows, no comma after “tree”—and not between the predicating verb and the direct object—the tree swallows a fence, no comma after swallows. The exception, of course, is when you’re using serial commas or parenthetical commas. The tree chews, swallows, and digests a fence. The tree, needing more iron, swallows.
The only other exceptions are maybe numbers and quotations, which are special situations. But even then, the comma serves the same role it has for more than half a millennium: to separate certain elements within a sentence. Just make sure not to separate the things that deserve to stay together.

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The Oregon State Guide to Grammar