When Are Em Dashes Used? A Practical Guide

Em dashes are used to set off parenthetical information, emphasize a word or phrase, clarify appositives that contain commas, introduce a list or explanation, or signal a sharp turn in thought. They create a stronger break than commas or parentheses and draw the reader's attention to the enclosed or following material. Use them sparingly to maintain their impact.

What Is an Em Dash?

An em dash (—) is a punctuation mark roughly the width of a capital letter M. It is longer than a hyphen (-) and an en dash (–). Unlike those marks, the em dash is primarily a stylistic tool for emphasis and clarity rather than a grammatical requirement. According to Grammarly, em dashes are used to add emphasis, set off extra information, or signal a break in thought. They can replace commas, parentheses, or colons, but they do so with a more dramatic effect.

When to Use an Em Dash

Em dashes are appropriate in several specific situations. The key is to use them intentionally, not as a default replacement for other punctuation.

To Set Off Parenthetical Information

Em dashes can enclose extra information within a sentence. Unlike parentheses, which tend to de-emphasize the content, em dashes make the inserted material more prominent. For example: "The conference—which was scheduled months in advance—was unexpectedly canceled." The University of Minnesota notes that em dashes are often used like commas and parentheses to set off parenthetical information, but they create a stronger break.

To Emphasize a Word or Phrase

An em dash can highlight a key point at the end of a sentence. For instance: "After months of preparation, the team achieved its goal—a perfect score." This use draws attention to the final element. Medium's handbook describes the em dash as a bridge that emphasizes whatever comes after it, like the pause before a punch line.

To Set Off Appositives That Contain Commas

When an appositive (a phrase that renames or describes a noun) already contains commas, using commas to set it off can confuse readers. Em dashes provide clarity. Example: "Three students—Alice, Bob, and Carol—won the science fair." Grammarly explains that em dashes help avoid comma clutter in such cases.

To Introduce a List or Explanation

An em dash can introduce a list or an explanation, similar to a colon but with a more informal or dramatic tone. Example: "The recipe requires three essential ingredients—flour, sugar, and eggs." This usage is common in creative and journalistic writing.

To Signal a Sharp Turn in Thought or Interruption

Em dashes can indicate an abrupt change in thought or an interruption in dialogue. Example: "I was going to—wait, what was I saying?" This use is more common in informal writing and fiction. The Australian Government Style Manual notes that two em dashes in a row are used to show a sudden interruption in quotations and reported speech.

Em Dash vs. En Dash vs. Hyphen

It's important to distinguish the em dash from similar marks. The hyphen (-) joins words (e.g., "well-known"). The en dash (–) is used for ranges (e.g., "pages 10–20") and connections (e.g., "New York–London flight"). The em dash (—) is used for the purposes described above. Merriam-Webster clarifies that em dashes are used in place of commas or parentheses to emphasize or draw attention to parenthetical or amplifying material.

Spacing and Style Considerations

Style guides differ on whether to include spaces around em dashes. The Chicago Manual of Style recommends no spaces (e.g., "word—word"), while the AP Stylebook uses spaces (e.g., "word — word"). Consistency within a document is key. Grammarly notes that spacing around em dashes is a style choice, but consistency matters more than the choice itself.

Common Mistakes and Overuse

Em dashes are powerful but can be overused. Too many em dashes can make writing feel choppy or overly dramatic. Medium's handbook warns against using em dashes excessively, as they can distract readers. Reserve them for moments that truly need emphasis or clarity. In formal writing, such as academic papers, use them sparingly.

How to Type an Em Dash

On most keyboards, you can type an em dash using shortcuts: on Windows, press Ctrl+Alt+Minus (on the numeric keypad) or Alt+0151; on Mac, press Option+Shift+Minus. In many word processors, typing two hyphens (--) will automatically convert to an em dash.

Em Dashes in AI-Generated Text

AI writing tools often produce em dashes frequently. If you find your AI-generated text has too many em dashes, you can revise the prompts to request fewer dashes or manually replace some with commas, parentheses, or periods. Grammarly suggests that clearer prompts or revision instructions can help manage em dash usage in AI text.