Updated May 2023
If you’ve been around long enough, you know that certain kinds of punctuation are trendy (hello, em dash!). And some are like the pets that you put in the backyard when company comes over (we’re looking at you, parentheses).
Dashes, commas, colons, and ellipses are often used to heighten drama in a sentence. But not always in a good way.
Let’s take a look at how each is properly used:
1. Comma. The most versatile of the marks is the comma. It wears many hats, but its two main functions are: (a) to set off nonessential expressions that interrupt the flow of thought and (b) to separate elements, thereby clarifying the relationship between them.
The comma is the most modest of the marks. It doesn’t draw undue attention to itself or to the material it sets off or separates. The comma is so common that usage examples would only elicit a chorus of “duhs.” Suffice it to say that as long as a comma doesn’t preempt a role specifically assigned to the colon, semicolon, or parentheses, it is generally the safe choice to set off information and separate elements. It might not be the flashiest choice, but it gets the job done.
2. Colon. The colon is straightforward in its application: It is used, as in this sentence, after an independent clause to (a) emphasize a word, phrase, or sentence which directly explains or illustrates the main clause or (b) introduce a list of items. Like an Army sergeant, the colon is focused and demanding. It calls out: Hey you—read this. Depending on its use, the first letter that follows the colon may or may not be capitalized. If either side of the colon can be its own sentence, the word after the colon is capitalized. If what follows after the colon is a list, then the words are lowercased.
3. Semicolon. The semicolon is arguably the only punctuation mark subject to long-running ridicule by the writing public. Kurt Vonnegut famously said the only reason to use one would be “to show you’ve been to college.”
Tsk-tsk, we beg to differ! It may be that the semicolon’s bad rap began with its naming. It should have been called the “semiperiod,” as it is used to join two independent clauses that could stand alone as sentences where either (a) a coordinating conjunction (and, but, or, etc.) or (b) a conjunctive adverb (however, therefore, etc.) has been omitted.
We like to think of the semicolon as providing a greater degree of intimacy and clarity, in the right circumstances, than would two distinct sentences. Consider this example: Susan loves pasta primavera; John does not. It is clear that John does not love pasta primavera. If the example is broken into two sentences, the expression becomes somewhat ambiguous: John does not—what?
4. Parentheses. Used to enclose explanatory material that is independent of the main thought of the sentence (that is, nonessential), parentheses can bracket a single word, a phrase, an entire sentence, a number, or a date (or just about anything else).
As with semicolons, they have their place, but overuse can imply mental laziness. Before using parentheses, it is wise to ask yourself if the material is important enough to be included without parentheses, and if it’s not, is it important enough to be added at all?
5. Em dash. Like parentheses, the em dash can set off nonessential elements; but it does the parentheses one better—it can also set off essential elements. Accordingly, the em dash, under the right circumstances, serves as an alternative to any of the other marks—the comma, colon, semicolon, and parentheses—as long as it is used sparingly and for special emphasis only.
6. Ellipses. It’s hard not to love an ellipsis. They’re so mysterious—the punctuation mark sitting at the bar with a dry martini and a secret past that everyone’s dying to know. An ellipsis is a slippery little devil, mostly used to mean, “Hey reader, you can guess where this is going, even though I’m not going to tell you…” When the ellipsis takes off its casual wear for a stint in a quoted sentence in a thesis or newspaper article, it means that material has been left out.
Deciding which mark to use
Is the pause you wish to create with a punctuation mark (and the information that will follow it) subject to the precise rules of the colon and semicolon? If so, use the appropriate one.
If not, ask yourself if the material to be added is essential or nonessential.
If essential, use the comma, or, if you really want to draw attention to it, use the more powerful em dash.
If nonessential, use the comma if you wish to discreetly add the information; parentheses if you wish to make it a bit more noticeable; and the em dash if you want to draw maximum attention.