On the English ACT, you’ll often see sentence interruptions.

A sentence interruption happens when a clause, word, or phrase is inserted into a sentence.

You’ll almost certainly encounter these on the English ACT.

Sentence interruptions can appear at the beginning or end of a sentence, or right in the middle. When a sentence is interrupted, there are three punctuation marks you can use. We’ll go through them from simplest to most complicated.

Commas in sentence interruptions

When you add extra (nonessential) information into a sentence, commas are usually the best choice.

My parents grounded me, deservedly, for a month.

Here, the writer adds the word “deservedly” to show they agree the punishment was fair. The sentence still makes sense without “deservedly,” so it’s nonessential and should be set off with commas.

Parentheses in sentence interruptions

Parentheses work in a similar way, but they create a stronger separation from the rest of the sentence. The ACT almost never tests parentheses directly.

My parents grounded me (I deserved it) for a month.

Dashes in sentence interruptions

Dashes create the strongest break. Writers often use them when the interruption has extra emphasis - maybe to make a point, add humor, or create a dramatic pause.

Here’s what you need to remember when using dashes on the English ACT:

• Just like parentheses, if you start a sentence interruption with a dash, you need to close it with a dash before the sentence continues.
• Unlike parentheses, if the sentence interruption finishes the sentence (so nothing comes after it), you close the sentence with a period or other ending punctuation mark like normal.

Correct example

My parents grounded me - for three whole years - for something I didn’t do.

Or:

My parents grounded me for something I didn’t do - for three whole years!

Both of these are good options.

Bad example

What you do not want to do is this:

My parents grounded me - for three whole years, for something I didn’t do.

This sometimes appears on the ACT as a wrong answer choice: the interruption starts with a dash but ends with a comma. Don’t fall for it!