Em Dash
The em dash is a flexible punctuation mark for strong breaks and parenthetical material. Microsoft style uses it for abrupt breaks, clarification, amplification, and parenthetical remarks, but warns against overuse and specifies no surrounding spaces for its house style.
An em dash can mark a strong break in thought, an interruption, or an emphatic parenthetical insertion. Spacing and some detailed conventions are style-specific.
Key details
Important caveats
Spacing Boundary
Spacing around em dashes varies by style; Microsoft style uses no spaces, so do not present one spacing convention as universal.
Usage Boundary
Do not overuse em dashes where ordinary sentence structure or lighter punctuation would be clearer.
Further guidance
Core Rule
Use an em dash when a stronger break than a comma fits the sentence and the chosen style permits it.
Practical Application
Use an em dash for a strong break, interruption, or emphatic parenthetical when that punctuation fits the house style. Do not use it automatically where a comma, colon, parentheses, or a new sentence would make the relationship clearer.
Reader Check
What relationship are you marking—interruption, abrupt shift, or emphatic insertion—and does the governing style permit an em dash there?
Worked Example
“The final shipment—the one delayed by customs—arrived Friday” uses paired em dashes for an emphatic insertion; a quieter parenthetical could use parentheses instead.
Sources and evidence
Sources are shown with the role they play in this guide. Historical or style-sensitive claims are kept within the evidence boundary described above.
- Dashes and hyphens — Microsoft Style Guide (opens in a new tab)Microsoft · En-dash and em-dash functions, including number ranges and sentence breaks