Punctuation

The dash

Dashes with parenthetical material for emphasis

A pair of dashes gives prominence to information that is not essential to the sentence but that you want to call attention to. The dashes are stronger marks than a pair of commas or parentheses.

Example sentence: Everything that went wrong – from the peeping Tom at her window last night to my head-on collision today – we blamed on our move.

Example sentence: The extreme outliers in the data set – with one observation at 18 rpm and another at 45 rpm – suggested the instrument was at fault and needed recalibration.

Dashes to set off appositives that contain commas

An appositive is a noun or noun phrase that renames a nearby noun. Nonrestrictive appositives are set off with commas. But when the appositive itself contains commas, a pair of dashes helps readers see the relationships among the sentence elements.

Example sentence: In my hometown, Peoria, the basic needs of people – food, clothing, and shelter – are less costly than in a big city like Los Angeles.

Dash to point toward a concluding element

A dash at the end of an independent clause can point toward and provide emphasis for a list, a restatement, an amplification, or a dramatic shift in tone or thought.

Example sentence: Along the wall are the bulk liquids – sesame seed oil, honey, safflower oil, maple syrup, and peanut butter.

Example sentence: Consider the amount of sugar in the average person's diet – 104 pounds per year, 90 percent more than that consumed by our ancestors.

Example sentence: Everywhere we looked there were little kids – a box of Cracker Jacks in one hand and mommy's or daddy's sleeve in the other.

Example sentence: Kiere took a few steps back, came running full speed, kicked a mighty kick – and missed the ball.

In the first two examples, the writer could also use a colon. The colon is more formal than the dash and not quite as dramatic.

Overuse of the dash

Unless there is a specific reason for using the dash, avoid it. Unnecessary dashes create a choppy effect.

Exercises:

Other punctuation marks 1

Other punctuation marks 2