February 12, 2016

Commas and periods are English’s most common punctuation marks. But the rules that apply to them are light years apart.

The rules for periods are pretty simple:

  • Periods appear at the end of a declarative sentence and in abbreviations
  • If an abbreviation ends a sentence, do not add a second period. The abbreviation’s period suffices.
  • Periods always go inside a quotation mark. Always. Those of you who put them outside routinely or occasionally, knock it off.
  • Likewise, use one punctuation mark to end a sentence. Do not use a period with a question or exclamation mark. (The exception is when you end a sentence with an abbreviation and a question or exclamation mark.)

And, that’s it.

Commas, however, have a slew of rules. And at least one rule is

complicated by the everlasting argument over the serial, or

Oxford, comma. We’ll revisit that argument at the end, because

many of you have tired of reading my serial rant on the serial


The other rules for commas are pretty straightforward, although

there’s disagreement on just how many rules there are.

Jane Straus, who literally wrote a book on punctuation, lists 16

rules with several sub-rules. Purdue University lists a mere 11. Utah Valley University rounds it down to 10.

I am not going to recite a comprehensive list. But here are a few I see violated often.

  1. Use commas between multiple adjectives before a noun—except when you don’t. Here’s the easy rule: If the adjectives in question can be reversed and the sentence still makes sense, you need comma to divide them. For example, in, “He was a spiritual, moral pope,” the comma is necessary because spiritual and moral could be reversed without changing the meaning of the sentence. But you wouldn’t use a comma to offset “cheap” and “winter” in the sentence, “He bought a cheap winter coat.”
  2. Yes, my dear friends, you must use commas to offset the person you are directly addressing. The only exception to that rule that I know of is when using the salutation “Dear Mr. Bhatia.” But use a comma in “Good morning, ladies and gentlemen,” and, “Maurice, you are the most arrogant man I know.”
  3. Which is correct here? “My brother Tommy stole your bookend”? Or, “My brother, Tommy, stole your bookend”? Trick question to illustrate that non-essential information is set off by commas but essential information is not. If I only have one brother, then the second example is correct because “My brother” and “Tommy” are the same person and “Tommy” is non-essential to understanding the meaning of the sentence. But if I have more than one brother, then the first example is correct because without naming Tommy you wouldn’t know which brother I was talking about.
  4. Like periods, commas always go inside quotation marks. Always. No exceptions.

If you learn those four rules and adhere to them consistently, you’ll be far ahead of most writers.

We now turn with glee to my serial comma rant and say goodbye to those who can’t take it anymore.

The serial comma rule states that in a list of three or more, a comma is placed at the end of the word before the conjunction. Therefore, in the sentence “I have three apples, two pears, and a partridge in a pear tree,” the serial comma comes at the end of “pears” and before the conjunction “and.”

Not everyone abides by the serial comma rule and the Associated Press Stylebook expressly limits its use to instances where leaving it out could lead to confusion. For example, in the sentence, “I had dinner with my parents, Pope Francis and Lady Gaga,” leaving out the serial comma could lead one to believe your parents are the pontiff and the lady.

I used to write that serial comma backers are zealots and those who don’t use them are laidback Californians, but I have a California friend who is as zealous in her non-serial beliefs as are serial punctuators. So I always use the serial comma when I write to her. It drives her nuts.

Personally, I don’t care if you use it or not. I only care that you use it or don’t use it consistently.

Ain’t English fun?

Tom Pfeifer is the managing partner and chief strategist for Consistent Voice Communications. Reach him at Tom@YourConsistentVoice.com.

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