Sentence interruptions
Also known as: nonessential elements, parenthetical elements
A sentence interruption is a word or phrase inserted into a sentence that adds extra, nonessential information. It must be set off by a matching pair of commas, dashes, or parentheses, and the sentence must still work grammatically if the interruption is removed.
A sentence interruption is a nonessential word, phrase, or clause dropped into the middle of a sentence to add detail, commentary, or clarification. In "My brother, a talented chef, is opening a restaurant," the phrase "a talented chef" interrupts the main sentence. The defining test: if you remove the interruption, the sentence must still be complete and grammatical — "My brother is opening a restaurant."
Interruptions are set off by one of three punctuation pairs: commas, dashes, or parentheses. Any of the three can be correct, but the punctuation must match on both sides. "The results — which surprised everyone — were published Friday" is correct; "The results — which surprised everyone, were published Friday" mixes a dash with a comma and is wrong. Commas are the most common and neutral choice, dashes add emphasis, and parentheses downplay the aside.
The trickiest cases involve deciding whether information is truly nonessential. Essential (restrictive) elements identify which noun you mean and take no punctuation: in "Students who skip class tend to struggle," removing "who skip class" changes the meaning. Nonessential elements merely add information about a noun that is already identified, so they take the paired punctuation.
The ACT English section tests sentence interruptions frequently. Questions typically ask you to choose punctuation that matches on both sides of an interrupter, or to recognize when a phrase is essential and needs no commas at all.
Key takeaways
- A sentence interruption adds nonessential information and can be removed without breaking the sentence.
- Interruptions are set off by matching pairs: two commas, two dashes, or parentheses — never a mix.
- Essential (restrictive) elements identify the noun and take no punctuation.
- Reading the sentence without the interrupter is the fastest way to check both the punctuation and the grammar.
- The ACT English section regularly tests matching punctuation around interrupters.