On ACT English, a dash does one of two jobs: a matching pair of dashes wraps around non-essential information the way a pair of commas would, or a single dash introduces something the way a colon would. Dashes feel mysterious because they show up so rarely in schoolwork, but they follow borrowed rules, which means you already know most of what you need. Throughout this article, dash refers to the long punctuation mark printed in a passage, not the short hyphen inside a word like well-known.
Job one: a pair of dashes around non-essential info
Take a sentence like Every senior on the roster, even the two who had never started a game, played in the final minute. The middle chunk is extra. You could lift it out and still have a working sentence, which is why it sits inside a pair of commas. Now picture that same sentence with a dash standing in for each of those two commas. It's equally correct, just louder. Dashes give the interruption more emphasis, and the ACT treats them as a legitimate alternative to commas in exactly this situation.
The deletion test works the same way it does for commas. If the sentence survives without the phrase, that phrase needs to be enclosed on both sides. If removing the phrase breaks the sentence, the information is essential and shouldn't be set off at all.
Job two: a single dash that introduces
A lone dash near the end of a sentence acts like a colon. It follows a complete clause and points forward to an explanation, a list, or a punchline. In There was only one thing left to pack: the tent. you could swap that colon for a single dash and the sentence stays correct. The requirement carries over too, so whatever sits to the left of the dash still has to be a complete sentence. If you want that rule in more depth, it's the same logic covered in how colons work on ACT English.
The matching pair rule
Here's the rule the ACT tests most, and it's the one worth memorizing word for word: the punctuation marks on both sides of a non-essential phrase have to match. You cannot open with a dash and close with a comma, and you cannot open with a comma and close with a dash. Two commas or two dashes, never one of each.
This is a gift, because you can often eliminate answer choices without reading the sentence for meaning at all. Find the opening mark, find the closing mark, and check whether they're the same. One caveat worth knowing: if the non-essential phrase ends the sentence, the period does the closing work, so a single introducing dash is fine there.
Correct versus incorrect
- Correct: The old theater, which had been closed for a decade, reopened in March. Also correct with a dash replacing each comma. Incorrect if you use a dash before which and a comma after decade, because the pair no longer matches.
- Correct: Marcus finally admitted what had been bothering him all week: he missed his old team. Also correct with a single dash in place of that colon, since the clause before it is complete.
- Incorrect: a dash placed after consists of in The exhibit consists of photographs, letters, and maps.The words before the mark don't form a sentence, so no dash and no colon belongs there.
- Correct: She packed light for the trip, one bag, one jacket, one pair of boots. reads better with a single dash after trip, which is a reminder that a dash can rescue a sentence where a comma feels too weak.
How the ACT tests dashes
Two patterns come up again and again. The first is the mismatched pair, where a choice quietly swaps one of the two marks. The second is a question where a colon and a dash both appear as choices doing the same introducing job. Since the two are interchangeable in that role, neither can be the answer, which lets you cross off two options instantly. Every English item on the enhanced ACT includes a question stem telling you what it's asking, so when a stem points at punctuation, you know to stop reading for style and start matching marks.
A quick self-check
When you see a dash in an answer choice, ask two questions in order. Is there a second dash later in the sentence? If yes, you're looking at a non-essential phrase, so mentally delete it and confirm the sentence still stands. If there's no partner dash, treat the mark like a colon and check that everything before it is a complete sentence. One of those two paths is always the right one.
Dashes are a small topic, and a focused half hour can put them behind you for good. thirty-six has concept quizzes that group punctuation questions by mark, so you can run a batch of dash questions back to back instead of waiting for one to appear. From there, it's worth reviewing how all five marks interact in the full ACT punctuation rules guide, since the ACT rarely tests any of them in isolation.
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