Punctuating Parenthetical Elements: Comma, Em dash, and Parenthesis

Parenthetical elements are words, phrases, or clauses that add nonessential information to a sentence, and these should be set off with a pair of commas, em dashes, or parenthesis. Follow along on how to apply them to your writing. 

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Side comments of a sentence are the little details that lean over and whisper something extra in the reader’s ear. In the world of English writing, we call these parenthetical elements. They add color to the text, but they are not the backbone of the thought.

If you lift them out, the sentence still stands upright. That’s the test: cross out the interruption, and if the sentence still makes sense, you’re dealing with nonessential information.

For example: “My sister, who just moved to New York, is starting a new job.” If we remove the clause “who just moved to New York,” you still have the heart of the matter: “My sister is starting a new job.” The rest is simply texture.

There are three graceful ways to cradle this extra information: two commas, two em dashes, or two parentheses. Think of them as three different melodies of voice.

• Commas are steady and polite, the everyday choice.

• Em dashes are dramatic; they sweep in with flair.

• Parentheses are softer, almost conspiratorial.

What you cannot do, however, is mix and match. You can’t open the door with a dash and close it with a comma. Parenthetical punctuation works in pairs. What you begin, you must properly finish.

A Pair of Commas

Let’s start with commas since they are the classic choice, the bread and butter of nonessential clauses. They slip into a sentence without fanfare, doing their job quietly. We, as readers, sometimes think they are not there.

Example: “The meeting, which was scheduled for Monday, has been postponed.”

If you remove the parenthetical element, the message still remains clear. The common mistake is forgetting to close what you opened. Just like this:

“The meeting, which was scheduled for Monday has been postponed.”

This leaves the interruption hanging midair. The same rule applies to single-word interruptions, like however.

Example: “The plan is ambitious. It will, however, require careful budgeting.”

Notice how however sits neatly between two commas, like a guest properly escorted in and out.

A Pair of Em Dashes

Em dashes are dramatic and not shy. They stride into a sentence with emphasis and a bit of a spotlight. See this example:

“The king picked Jason—bless his brave soul—to lead the infantry.”

The meaning is the same as with commas, but the rhythm changes. The interruption feels sharper, more pronounced. Dashes are wonderful when you want the inserted detail to stand out, to carry a little extra weight. That said, not everything calls for drama. Single transitional words like however prefer commas. Writing “It will—however—require careful budgeting” is a step too far. We suggest using a pair of commas for single-word interruptions unless it is onomatopoeia.

“The door slammed shut—bang—and the argument ended just like that.”

A Pair of Parentheses

Parentheses are the gentlest of the three. They feel like a side note scribbled in the margin. The information is there, but it doesn’t demand attention. One thing to remember: a comma should never appear right before an opening parenthesis.

Examples: This is used to describe either emotions (love or excitement) or small, everyday habits (e.g., sipping coffee, doodling).

Incorrect: It can describe feelings, (pride in finishing a long project) or quiet wonder (staring at stars on a crisp winter night).

In writing, it is not very strict with choosing between commas, dashes, and parentheses. Commas keep things balanced and professional. Dashes inject drama and emphasis. Parentheses soften the blow, making the addition feel optional, almost like an afterthought.

No matter your choice, the golden rule holds steady: The information must be removable without collapsing the sentence’s meaning. If the sentence can walk on its own, then the parenthetical element is doing exactly what it should.

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