ACT® · English: Punctuation Conventions
Dashes and Parentheses for Complex Parenthetical Elements
Dashes and parentheses do the same job as paired commas — setting off extra information — but they turn up the volume, especially when the interrupter already has commas inside it.
Commas, dashes, and parentheses can all set off an interrupter — a phrase that could be lifted out without breaking the sentence. They differ in volume, not grammar. Commas are quiet and standard: 'The speaker, a former mayor of the city, addressed the delegates.' Parentheses whisper, marking the aside as almost optional, extra trivia. Dashes shout: they make the interrupter feel dramatic or emphatic, and they're the tool to reach for when the interrupter itself contains commas, since stacking commas on commas gets confusing fast. 'The delegates — most of them first-time attendees — filled the hall' uses dashes precisely because 'most of them first-time attendees' could otherwise tangle with surrounding commas.
Whatever mark you choose, both sides have to match: two commas, two dashes, or two parentheses — never a mix, and never a dash paired with a comma. The one exception is position. When the set-off material sits at the very end of the sentence, the period itself acts as the closing edge, so only one dash is needed: 'The council rejected all the bids for one reason — cost.' That's not an exception to the pairing rule so much as the sentence running out before a second mark is needed.
Don't confuse a dash with a hyphen. A hyphen glues words into a compound, like first-time, with no space on either side. A dash is a full punctuation mark that separates a phrase from the rest of the sentence, and on a keyboard it's typically written with spaces around it. Mixing them up is a common flag: a hyphen can never do a dash's job of isolating a whole clause or phrase.
Key terms
- Interrupter
- A word, phrase, or clause that adds extra information but could be removed without breaking the sentence.
- Dash
- A long horizontal mark used, often in a pair, to set off a phrase with more emphasis than commas.
- Hyphen
- A short mark that joins words into a single compound, like first-time, with no surrounding spaces.
- Parentheses
- A pair of curved marks that set off material as a quiet, optional aside.
Watch it explained
- How it worksHow do commas, dashes and parentheses set off the same interrupter at three different volumes?
- Worked exampleWalk me through setting off 'a former mayor' inside 'The speaker a former mayor took the podium.'
- Worked exampleFind the strongest marks to use when an interrupter already contains commas of its own.
- Common mistakeWhy isn't a dash interchangeable with a hyphen, given that both are short horizontal lines?
- Going furtherWhat changes when the material being set off lands at the end of a sentence rather than the middle?
Check yourself
End of topic.