Understanding Parenthetical Elements

A parenthetical element is a word or group of words that interrupts the flow of a sentence and adds additional (but nonessential) information to that sentence. This element can be long or short, and it can appear at the beginning, the middle, or the end of a clause or sentence.

• John, the second batter in the lineup, is a fast runner.
• Mildred is an excellent cook, as a matter of fact.
• Just this once, you should try mustard on your peanut butter sandwiches.
• The dog, after guarding the chewed-up toy for more than an hour, finally got tired of waiting for me to play with him.

Types of Words or Word Groups that Can Be Parenthetical Elements:

• Appositives

Example: The book, a 758 page monster, was required for my history class.

• Relative clauses

Example: My professor, who eats lunch every day promptly at noon, was not available for discussion.

• Prepositional phrases

Example: The turkey, after moments of deliberation, ate the bug.

• Phrases as examples

Example: Foods that are hot or spicy, e.g. jalapenos or hot wings, make my eyes water.

You might think of the parenthetical element as a sudden thought that pops into your head as you are making a statement. Because it provides additional or supporting information to a complete sentence, the main part of the sentence should be able to stand alone without the words stated in the parenthetical element.

The name parenthetical might cause confusion because it resembles the word parentheses. In fact, some parenthetical elements are so strong (they can be quite jolting) that they require parenthesis. The previous sentence provides an example! Here are a few more:

My sister (the one standing on the chair) is trying to get your attention.

The strawberry tart (the one with the bite taken out of it) belongs to me.

Yesterday (the longest day of my life) I got my first speeding ticket.

Punctuation for Parenthetical Elements

The examples above show that parenthetical elements are usually set off by some form of punctuation in order to avoid confusion. The type of punctuation used actually depends on the degree of interruption caused by the interrupter.

Commas are used when the interruption is least emphatic. If the sentence containing the parenthetical element flows pretty smoothly, then commas are a good choice:

• My friend, who doesn’t like to wear socks, is trying to give me his tennis shoes.

Parentheses are used (as stated above) when the interrupting thought represents a bigger diversion from the original message or thought.

• Pizza is my favorite food (the brick oven kind is best).
• I think I'll go home now (the walk will do me good) before I fall asleep on the job.

But there is one more form of punctuation that you may use if you use an interrupting parenthetical element that really jolts the reader from the main thought. Dashes are used for the most emphatic interruptions. Use dashes to set off a parenthetical element for a more dramatic effect. 

My birthday party—what a surprise!—was a lot of fun.

The frog—the one who jumped on the window and made me jump a mile— is now under my chair.

I bit my lip—ouch!—to keep from speaking my mind.