Typographic Punctuation: The Em Dash

Character Representation and Length

The em dash (-) is a punctuation mark significantly longer than a hyphen (-). Its length is typically equal to the width of a capital "M" in the current typeface, hence its name. It differs visually from the en dash (–), which is approximately half the width of an em dash.

Usage and Function

The em dash serves multiple grammatical purposes, primarily indicating a break in thought or sentence structure. It can also set off parenthetical phrases or appositives, offering a more emphatic separation than parentheses or commas. Its use often enhances readability and emphasizes specific elements within a sentence.

Input Methods Across Platforms

Keyboard Shortcuts

Several keyboard shortcuts exist depending on the operating system and applications. Common methods include:

• Option + Hyphen (MacOS): Holding down the Option key while typing a hyphen produces an em dash.
• Alt + 0151 (Windows): Holding down the Alt key and typing 0151 on the numeric keypad generates an em dash. This method may require the Num Lock to be enabled.

Character Map or Character Palette

Operating systems provide character map or character palette tools allowing the selection of special characters, including the em dash, from a visual list.

Word Processors and Text Editors

Many word processing and text editing applications offer auto-correction or auto-replacement features that convert two hyphens typed consecutively (--) into an em dash. The specific behavior may depend on the application's settings.

HTML Entity

For web development, the em dash can be inserted using the HTML entity —.

Typographic Considerations

Consistent spacing around the em dash is crucial for proper typographic style. Typically, no space is used before or after the em dash.

Alternatives to the Em Dash

Depending on context, parentheses, commas, or colons might serve as viable alternatives, though the em dash often provides a more stylistic and emphatic separation.