Commas, semicolons, and colons—oh, my!

Specifics about how to use these three punctuation marks can be confusing. Here’s some help.

You probably cannot imagine distributing a press release or mailing a “Dear Investor” letter that includes a typo, but most communication professionals have experienced the embarrassment of doing just that.

Punctuation errors can be as easy to overlook as the misspelling that lingered through two versions of that white paper before your colleague caught and corrected it. That’s why it is so important to understand when to use the comma, the semicolon, or the colon in your writing—before you press send, publish, or “remove from hold.”

Communicating with commas

A 1965 Warriner’s textbook lists the comma as the most frequently used punctuation mark, and many writers have a tendency to overuse it. In November, the Grammarly team polled more than 1,700 job-seekers and professionals on what punctuation they most like to include in their writing. The semicolon (13 percent), em dash (10 percent), and period (8 percent) were top contenders; yet, overwhelmingly we learned that English writers are most thankful for the comma (45 percent).

However, misuse of commas is among the top grammar mistakes that writers around the world are making, according to a recent audit of English writers. When all is said and done, there are 28 different types of comma mistakes that English writers can make.

One of the most common comma debates involves the serial comma, which separates simple subjects in a sentence:

“Mike’s pens were blue, red, and purple.”

The AP Stylebook asserts that we do not need to include a comma after the word red, but “The Elements of Style” says the comma belongs there. Warriner’s breaks the tie by suggesting that—although both ways are correct—writers should put that final comma into the sentence to avoid confusion. Without the comma, after all, it could be implied that Mike’s pens were both blue and red with purple polka dots. (Editor’s note: sees the serial comma as a necessary evil, aesthetically unpleasing but necessary often enough that its use is warranted. For the sake of consistency, we use it in all simple series.)

It seems that the serial comma is a matter of a style. The more frustrated writers among us call it a gray area. Independent clauses in a series are another gray area. Though typically separated by a semicolon, they can also be separated by a comma, depending on their length and on the inclusion of a conjunction, such as and. Here’s an example:

“We wrote, we revised, we copy-edited, and we hit ‘send.'”

The same sentence could also employ semicolons; however, because the phrases are so short, that would be less widely accepted.

Parenthetical expressions are also tricky. “The Elements of Style” and Warriner’s agree that a rule is hard to apply. All four of these sentences are correct:

“This is indeed a glaring mistake in your copy.”

“This is, indeed, a glaring mistake in your copy.”

“We therefore want you to revise it immediately.”

“We, therefore, want you to revise it immediately.”

Warriner’s explains that “the author’s intention is the determining factor governing the punctuation. If he wishes the reader to pause, to regard an expression as parenthetical, he sets it off; if not, he leaves it unpunctuated.” Again, this is a matter of style.

Sizing up semicolons

The semicolon demonstrates a close relationship between two sentences or two independent clauses.

In the example below, either sentence is correct. According to Strunk and White, the first use case “suggests the close relationship between the two statements in a way that the second does not attempt. . . . Indeed, the simple method of indicating relationship between statements is one of the most useful devices of composition. The relationship . . . is commonly one of cause and consequence.”

“I thought my colleague’s copy was simple-minded; this left me in a quandary as to what to tell her.”

“I thought my colleague’s copy was simple-minded. This left me in a quandary as to what to tell her.”

A more mundane, but necessary use of the semicolon is to separate items in a series when the items contain commas in their descriptions.

“For the book launch, we visited a few schools in upstate New York: Hamilton College, Clinton; Cornell University, Ithaca; and Union College, Albany.”

Composing using colons

The colon satisfies two primary needs. The first is to present a list (as long as the list isn’t introduced by a verb or preposition).

“At the press briefing, I saw immediately that the caterer had forgotten essential items: cocktail napkins, bottled water, and ice.”

The second way to use a colon is for emphasis, as it tends to jolt the reader.

“I had captured the audience’s attention: I whispered.”

Writers also use the colon to introduce longer quotations, those of more than one sentence. Remember to capitalize the first word after a colon if it starts a complete sentence.

My colleague told me: “At the writers’ conference, I gazed upon the stage and saw my favorite authors. My entire editorial staff was impressed, too.”

Take the time to get it right

We pride ourselves on being effective communicators, but on deadline, banging out copy, we might add too many (or too few) commas to a series. Or maybe we’ll forget whether we should use a comma or semicolon, or whether to capitalize the first word after a colon. After all, we’re all human.

Reading a finished piece slowly out loud lets you hear the rhythm of your writing and gives you a chance to double-check whether you’ve used a comma to pause, a semicolon to connect two closely related sentences, or a colon for emphasis. Above all else, it provides another way for you to check your writing for simple mistakes—and for stylistic choices.

A self-proclaimed word nerd, Allison VanNest works with Grammarly to help perfect written English. Connect with Allie, the Grammarly team, and more than 500,000 Grammarly Facebook fans at

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This article originally ran on in January 2013.

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