8.10 Punctuation: Commas
When it comes to using commas, you have likely heard the guideline to ‘place a comma wherever there’s a pause.’ This advice is helpful to a degree, but it’s important to understand some of the rules that govern that advice. However, it can seem daunting as a writer to learn and apply the seventeen or so rules for comma usage, so we’re only going to look at a few of the most common ones. It’s helpful to remember the comma’s primary function: it separates. The comma separates complete ideas, descriptive phrases, items in a list, and before and after most transition words.
RULE 1. Use commas to separate independent clauses when they are joined by any of these seven coordinating conjunctions: for, and, nor, but, or, yet, so (FANBOYS). The comma comes after the first clause and before the conjunction.
EXAMPLES:
| The game was over, but the crowd refused to leave. |
| The student explained her question, yet the instructor still didn’t seem to understand. |
| Yesterday was her brother’s birthday, so she took him out to dinner. |
RULE 2. Use commas after introductory clauses, phrases, and words that come before the main clause.
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- Introductory clauses:
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EXAMPLES:
| While I was eating, the cat scratched at the door. |
| Because her alarm clock was broken, she was late for class. |
| If you are ill, you ought to see a doctor. |
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- Introductory phrases (note how the main subject and verb follow the comma):
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EXAMPLES:
| Having finished the test, he left the room. |
| To get a seat, you had better come early. |
| After the test but before lunch, I went jogging. |
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- Introductory words:
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EXAMPLES:
| Well, perhaps he meant no harm. |
| Yes, the package should arrive tomorrow morning. |
| However, you may not be satisfied with the results. |
RULE 3. Use commas in the middle of a sentence to separate nonessential clauses, phrases, and words. Use one comma before to indicate the beginning of the pause and one at the end to indicate the end of the pause.
EXAMPLES:
| Clause: | That Tuesday, which happens to be my birthday, is the only day when I am available to meet. |
| Phrase: | The food, on the other hand, is rather bland. |
| Word: | This time, however, you seem to be falling behind. |
*NOTE: To determine if a clause, phrase, or word is essential, ask yourself if the sentence still makes sense if you leave it out. If it does, then it’s nonessential and should be set off with a pair of commas. Nonessential elements are sometimes called parenthetical.
RULE 4. Use commas to separate three or more words, phrases, or clauses written in a series.
EXAMPLES:
| The Constitution establishes the legislative, executive, and judicial branches of government. |
| The candidate promised to lower taxes, protect the environment, reduce crime, and end unemployment. |
*NOTE: The comma before the and at the end of a list is called an Oxford Comma; some writers choose to leave off the final (Oxford) comma in a series. For example, in both of the s