A subtle difference: Em dash vs. colon

When speaking, we can convey our emotions by changing the tone of our voice or the length of our pause. When writing, however, we in part convey that emotion with punctuation. Unfortunately, the em dash and the colon are often confused because of the subtle difference in emotion each delivers.

An em dash is the long line that appears between two words, as in Though Houston is Texas’s fourth most populous city, one metro area in the state actually is larger—Dallas-Fort Worth. The colon is a dot atop of another dot and also appears between two words, like Three cities in Florida boast populations exceeding 300,000: Jacksonville, Miami, and Tampa. Both show that words related to the main portion of the sentence are to follow.

Emotion-wise, the dash typically is used when those related words are of a dramatic nature. It creates a strong break in the structure of a sentence, usually to emphasize some startling point or as an aside. Hence, You’re not going to believe where Nate and Lizzie went on their honeymoon—Paris!

The colon, however, shows that the related words are merely informational, usually defining or listing examples, and is emotionally neutral. To wit, The three most populous cities in the United States are: New York, on the East Coast; Los Angeles, on the West Coast; and Chicago, in the country’s center. Note that if you have a list of items that make use of a comma when following a colon, separate each listed item with a semicolon.


My name is Rob Bignell. I’m an affordable, professional editor who runs Inventing Reality Editing Service, which meets the manuscript needs of writers both new and published. I also offer a variety of self-publishing services. During the past decade, I’ve helped more than 300 novelists and nonfiction authors obtain their publishing dreams at reasonable prices. I’m also the author of the 7 Minutes a Day… writing guidebooks, four nonfiction hiking guidebook series, and the literary novel Windmill. Several of my short stories in the literary and science fiction genres also have been published.